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Little Boy Lost

Kate Snow reports from inside the family circle of missing 7-year-old Kyron Horman to bring viewers the latest developments in the case, and an emotional and candid interview with his biological parents, Kaine and Desiree. In addition, she speaks exclusively to Desiree and her husband, Tony, who brings a detective's take to how this case has unfolded over the last seven weeks.

One moment he was a proud second grader presenting a class project; the next he was gone.

DESIREE YOUNG: I said, `I don't understand.'

Seven-year-old Kyron Horman simply disappeared from school. Left behind: his blended family, united.

TONY YOUNG: Kyron, we miss you.

What no one saw coming was that this family would start to doubt one of their own.

KYLE IBOSHI: Everything that we have heard suggests that Terri Horman...loved her stepson Kyron.

So why did so many suddenly have questions about this stepmom? Little things at first.

KATE SNOW: You kind of seemed to stiffen a little bit.

DESIREE YOUNG: Yeah.

One by one, three parents becoming concerned about the fourth.

TONY YOUNG: I thought that something must not be right.

Then, a stunning revelation.

KATE SNOW: Do you think she is capable of hurting a child?

KAINE HORMAN: Based on what I know now...I think anything is possible.

Tonight, the very latest on the search and the investigation. Little Boy Lost.

Part 1:

ANN CURRY: Good evening and welcome to DATELINE. I'm Ann Curry. You may have heard about Kyron Horman, the little boy who disappeared from his school in Oregon last month. There's been a massive search and ongoing investigation. His family, which started out united in trying to find him, now finds itself torn apart. Tonight, new details on why Kyron's parents, who might have found solace within the family's ranks, have instead found cause for suspicion. Here's Kate Snow.

Kyron Horman, the seven-year-old boy whose crooked smile showed the world the Tooth Fairy had just paid a visit and made parents across the country stop to hug their own kids close.

GINA ZIMMERMAN: [newscast] Everybody's in shock that this could happen in our little school that we all—everybody knows everybody.

That gap-toothed grin of Kyron's now covers billboards, T-shirts, fliers. From the moment he went missing, the boy in the photo brought out hundreds of people combing through the dense forest near his school and home, working around the clock to find the missing second grader alive.

UNIDENTIFIED MAN #1: Any small tidbit of information...

UNIDENTIFIED MAN #2: Kyron!

KAINE HORMAN: He's not there with us, so it's still pretty empty.

Tonight, Kyron's biological parents, Kaine and Desiree, and Desiree's husband, Tony, speak out – what it's like to lose a precious little boy.

KAINE HORMAN: Where did he go? What—how come no one knows where he is?

The pain, the guilt. How do they keep their hope?

DESIREE YOUNG: It's hard because he's not here, but it's also comforting to have his stuff around, too.

And what happened to make them suspicious of one of their own.

DESIREE YOUNG: I don't care if they ask you to take 10 polygraphs, you've got to do it.

We go inside the family circle in this time of crisis to bring you the latest twist in a surprising, often stunning story.

KYLE IBOSHI: What's going on behind the scenes? What's going on in the Horman home?

The sheriff's department says it's tracked more than 3,000 leads. They say they continue to make significant progress, but as of tonight Kyron Horman is still a little boy lost. He's only seven, a bit shy –awkward even. The kind of little guy who's just starting to discover his world. His mother, Desiree, and his father, Kaine, by his side along the way.

KAINE HORMAN: He's the kind of son that every father hopes they're going to have.

DESIREE YOUNG: He likes to get dirty. He's definitely a typical seven-year-old that gets dirty all the time.

Kyron's parents shared their photo album, a treasure trove of memories, hundreds of images from Kyron's childhood. It's hard to spot a single one where he's not smiling as you trace the seven years of Kyron's life, all the way back to day one.

DESIREE YOUNG: When he was born, he took quite a while. He just didn't want to come out. And when he finally came out, he peed.

KATE SNOW: As boys do.

DESIREE YOUNG: Yes. And the doctor said, ‘OK, well, the plumbing works.’

KATE SNOW: You remember that day, Kaine?

KAINE HORMAN: Yeah. And the birthing classes we had gone to, the instructor there had recommended for dads, in order to get closer with your—with your child, they actually encourage you to take your shirt off and hold your baby close so they can get your smell.

KATE SNOW: Took off your shirt and held him real close.

KAINE HORMAN: Held him close, and it's really been that close of a bond ever since.

It's a bond that stayed strong through a family shake-up early on.

KATE SNOW: You two separated somewhere around the birth of Kyron.

DESIREE YOUNG: Mm-hmm.

KAINE HORMAN: Mm-hmm.

Kaine and Desiree both remarried, Kaine to Terri Horman, and Desiree to Tony Young. In this new blended family, Kyron's two parents became four, and he now had two older brothers, Desiree and Terri's older sons from previous marriages. And then, about 20 months ago, Kaine and Terri had a little girl, Kiara.

KATE SNOW: Like so many American families, you have this –

DESIREE YOUNG: Yeah.

KATE SNOW: – kind of stepfather-stepmother-mom-dad extended family. How did that all work in raising Kyron?

DESIREE YOUNG: We just made sure that we got along, and that we sacrificed things that needed to be sacrificed for the good of the kids, and just dedicated our emotional energy in that and not at each other.

They got along as best they could. Around the age of two, Kyron began living with his father and stepmother full time in Portland. Friends say Terri was an attentive stepmom, active in Kyron's school.

KATE SNOW: Was she a good mother?

DESIREE YOUNG: I wouldn't say she would replace me, obviously, but she definitely gave him what he needed.

Kyron's mom would visit him often in Portland, or Kyron would make the trip on weekends and holidays to her house five hours south in Medford, Oregon. The years flew by, and Kyron grew up. Here he is whistling at a school concert, and here reading a school report on bridge construction.

By second grade, science and math were his favorite subjects, and he loved to tell everyone about the things he was learning.

KAINE HORMAN: He has a great personality, and he's just so much fun to have around. The happy noises that come from him, and the constant, you know, questioning that a seven-year-old has, the curiosity.

KATE SNOW: Sense of humor?

DESIREE YOUNG: Yeah.

KATE SNOW: Tell jokes a lot?

DESIREE YOUNG: He's funny, yeah. He catches things that you don't think he catches, and comes out of his mouth, and you just look at him and laugh. ‘Where did you get that?' And he...

Desiree's sister, Kelly Ramirez, remembers that smile.

KELLY RAMIREZ: He lost all his teeth so early he just had all these crazy teeth growing in at the same time, and he would just smile at you with that smile, and it—you couldn't help but smile back.

Kyron loved going to school, especially riding the bus to join the other second graders in Ms. Porter's class at Skyline Elementary, a small school nestled in the rolling farmland and woods beyond the hills west of downtown Portland. In June, Kyron's school year was coming to a close. Kyron's mom, Desiree, says the family was looking forward to big summer vacation plans.

DESIREE YOUNG: And we had a—quite a few trips planned. We have a houseboat reserved for August, and he's going to be home before then. But we also have a lot of camping trips planned, and he had a trip down to California planned, and...

KATE SNOW: Lots of plans?

DESIREE YOUNG: Yeah.

KAINE HORMAN: Yeah.

KATE SNOW: And you still have them?

DESIREE YOUNG: Yeah.

KAINE HORMAN: Yeah.

But seven weeks ago, those plans were put on hold when Kyron Horman didn't get off the bus after school and seemed to vanish without a trace.

Coming up, Kyron isn't on the bus or anywhere else.

KAINE HORMAN: That's when the panic started to set in.

When Little Boy Lost continues.

Part 2:

Seven-year-old Kyron Horman never seemed to go anywhere without a grin on his face, and, on one particular day this past June, the kid who loved science and the outdoors had one more reason to smile.

Here at Skyline elementary, it's quiet now. Summer vacation is well under way. But back on the morning of June 4th, the staff here was getting ready for one of the biggest days of the year, the school science fair.

Just a few miles away, Kyron was at home getting ready for school. He was excited, couldn't wait to show everyone his colorful diorama about the red-eyed tree frog. He'd worked really hard on it, and his dad knew it.

KAINE HORMAN: And just told him I was really proud of all the effort he put in on his project, he did a really great job, and gave him a big hug.

KATE SNOW: Did you tell him you loved him?

KAINE HORMAN: I did.

Kaine left for his job as a software engineer at Intel. Kaine's wife, Terri, Kyron's stepmother, took Kyron to school in her white pickup truck. They went early so they could tour the science fair exhibits together with other parents and kids before the first bell. School spokesperson Erin Barnett:

ERIN BARNETT: It's an opportunity for the parents to be there with their children, and go in between the classrooms and seeing the different exhibits, and taking pride in their child's accomplishments, and I think this is a—just a very, very proud morning for Kyron.

Later that day, Kyron's stepmom, Terri, posted this photo on her Facebook account of her beaming stepson next to his completed science project.

ERIN BARNETT: Staff saw him, you know, with his stepmom and, you know, looking at his exhibits and, you know, just like the other families who were here.

Then the morning bell rang. The regular school day was beginning. Time for kids to head to their classrooms and for their parents to start to filter out. A routine part of the day that would later become a critical moment for investigators.

Terri Horman said around 8:45 in the morning, the last time she saw her stepson Kyron, he was walking down this hallway in his school on his way to his second grade classroom.

It's unclear exactly who, if anyone, saw him after that point, or where, but Ms. Porter started class as usual, reading group, then recess, then lunch. At some point in the day, Kyron was marked absent. At 3:00 PM, it was time for the school buses to line up. Kids tired from a full day filed on board and plopped down in their seats, all but one.

KATE SNOW: Do you remember going out with your daughter to meet the bus?

KAINE HORMAN: Mm-hmm. I remember the time like it was yesterday when we, you know, went downstairs and got her and put her shoes on, and her and I started walking down the driveway to go meet him at the bus.

KATE SNOW: And he wasn't there?

KAINE HORMAN: Nope.

KATE SNOW: Did you know something was wrong right then, or did you think, ‘Well, maybe he's just back at school, expecting me to pick him up'?

KAINE HORMAN: That's what I had thought originally, so I just thought, well, it's a mistake. We'll go get him. And then the bus driver called up to the school to double-check because he wasn't on the bus, and so she called the school to see where he was, and they said he hadn't been at school all day. And that's went the panic started to set in.

Kaine says he and his wife, Terri, jumped into their car and raced the few miles to the school.

KATE SNOW: Do you remember the words you exchanged? Do you remember that moment?

KAINE HORMAN: Not really. I don't remember much of the conversation other than just, ‘Where could he be? What happened today? You know, you dropped him off at school.' Just kind of walking through her morning, but it was so quick because we were at the school within about five minutes, so there wasn't a lot of dialogue.

Five hours south in Medford, Oregon, Kyron's biological mother, Desiree, was about to get looped in to the nightmarish reality developing at her son's school.

DESIREE YOUNG: I got a phone call from the school, and she said, ‘Is this Desiree Young?' And I said, `Yes it is.' And she said, `You're listed as the emergency notification for Kyron Horman?' And I said, `Yeah, he's my son. What could I do?' And she said, `I have to notify you, he's missing.' And for a split second I thought it was a joke, and I said, `What?' She said, `He's missing.' I said, `I don't understand. How could he be missing?' I said, `OK, where is Terri and Kaine?' `Well, Terri's here.' `All right. Thank you.' And I hung up with her, and immediately called Terri, and I cussed a little bit, said, `What the hell's going on?' And she said that they went to the science fair and everything was fine and she waved goodbye to him, and he went into his class, or so she thought.

But even in those first hours of crisis, Desiree had an unsettling feeling that maybe she wasn't hearing the full story.

DESIREE YOUNG: There was just something in my gut that just didn't feel good.

Coming up, it's not just Desiree starting to wonder. As Terri keeps talking to investigators, others become suspicious about her story, too.

TONY YOUNG: There's starting to be some structural problems with what she's saying at that point.

When Dateline continues.

Part 3:

Kyron's father, Kaine Horman, was in a panic. His son should have been on the bus that afternoon of June 4th, but he wasn't there. The bus driver called back to the school and found out he had been marked absent hours before. This wasn't just a temporary mixup; Kyron was really missing. The school's secretary dialed 911, and then an automated call went out to parents in the Portland school district.

UNIDENTIFIED MAN #3: Skyline second grader Kyron Horman did not arrive home from school today.

That call set off shock waves of disbelief. A child had disappeared right from under everyone's nose in what is supposed to be a safe place for kids: school.

As search teams started combing the area, Kyron's mother, Desiree, and her husband, Tony, raced up to Portland from their home in Medford, Oregon. When they heard the awful news, they called Kyron's stepmother Terri Horman just before jumping in the car.

DESIREE YOUNG: I had told her, `I'm coming up there.' And she said, `You are?' And she seemed surprised at that, which I thought was strange. I said, `Of course I am. I'll be there in, you know, four, four and a half hours.'

As night fell, the search continued outside Skyline School with flashlights and dogs, but something was also brewing inside the Hormans' house, where all four parents were gathered together: Kaine and Terry, Desiree and Tony. Tony has had a unique perspective from day one. He's not only Kyron's stepfather, he's also a police detective back in Medford. And tonight, he's speaking out for the first time.

TONY YOUNG: I was watching the investigation right from the start.

Tony says that first night, because he knows so much about how police operate, he was walking the family through what to expect.

TONY YOUNG: I explained to each person that now our lives are not private anymore, that the investigators are going to want to know very detailed information about our lives.

That's when Tony noticed something unsettling. He says Terri, Kyron's stepmom, seemed to bristle at the idea that she would be questioned.

TONY YOUNG: She instantly started to express some displeasure at that, and not wanting—feeling like she was persecuted. And I thought that was kind of an unusual reaction that early.

But Tony says he wanted to keep an open mind, and the goal, of course, was finding Kyron. The question: Did he wander off, get lost or hurt in the rough terrain around the school?

GINA ZIMMERMAN: [newscast] He's just a very timid, sweet boy.

Gina Zimmerman, a parent from Skyline, says the Kyron she knows would never just walk out of school, especially on such an important day.

GINA ZIMMERMAN: [newscast] He did the red-eyed frog. He was very proud of it and wanted to be there. So there—it was—he would not have left to go wander around.

But what if he didn't leave alone?

On that busy morning here at Skyline Elementary, could someone, a stranger, have slipped Kyron out of the building without anyone noticing? It's a small school, but there are eight doors in and out, most of them unmonitored.

Concerned and baffled neighbors, friends and parents flocked to Skyline Elementary, wanting to do something, anything to help find Kyron. And on the one-week anniversary of his disappearance, Kyron's parents, all four, appeared in public for the first time.

TONY YOUNG: [press conference] Kyron, we miss you, we love you, and we need you home right now.

KAINE HORMAN: [press conference] Please help us bring Kyron home.

Members of the family stood side by side, a unified front – but look closely and you can see some interesting body language between Kyron's mother, Desiree, on the left in the sweater, and his stepmother, Terri.

KATE SNOW: She reached—she put her arm around you at one point?

DESIREE YOUNG: Mm-hmm.

KATE SNOW: And you kind of seemed to maybe stiffen a little bit.

DESIREE YOUNG: I don't know. It's a little strange for your ex-husband's new wife to be hugging you and caressing you. It just seemed strange to me.

That strange feeling for Desiree had been steadily growing into full-blown suspicion. It started when all four family members submitted to lie detector tests. Tony tells Dateline he noticed right away that something wasn't gelling for detectives because they asked Terri Horman to submit to a polygraph more than once.

TONY YOUNG: I thought that something must not be right, something must not be allowing them to check her off their list.

KATE SNOW: Isn't it possible, though, that she was just nervous, that she didn't pass her lie detector test with flying colors because she was emotional or upset or nervous?

TONY YOUNG: There's more to it than just that. The information that you're giving, does it—does it hit your ear and sound right? Does it make sense?

KATE SNOW: She wasn't making sense?

TONY YOUNG: Not from the information I heard from her.

A source close to the family says Terri complained the polygraph test made her feel like a criminal. Investigators, she said, were aggressive and tried to rattle her. Tony and Desiree say the biggest question marks revolved around Terri's whereabouts that morning that Kyron went missing.

DESIREE YOUNG: She couldn't explain to them for about two hours worth of time where she was or what she was doing.

And there was something else that gave Desiree and Tony a sinking feeling that something wasn't right. They say Terri's cell phone records apparently didn't match up with where she said she was on the morning of Kyron's disappearance.

TONY YOUNG: That to me is strike two. That's huge… There's starting to be some structural problems with what she's saying at that point. And then it continues to stack up.

Strike two. And with that, Desiree and Tony began to put pressure on Terri to talk with investigators again, tell them everything she knows.

DESIREE YOUNG: I tried to use my mother card, from one mother to another. I tried to get her to understand that if the tables were turned and I was the last person seen with Kiara, would she not want me to do everything possible to bring Kiara home? And she said, ‘Of course.’ I said, ‘OK, then, you've got to cooperate with them. And I don't care if they ask you to take 10

polygraphs, you've got to do it. It's just the right thing to do, for Kyron.'

KATE SNOW: Is that one of the last times you spoke to her?

DESIREE YOUNG: Yeah.

Despite Desiree and Tony's suspicions in private, in public the four parents stood together again two days after their first appearance and listened to the sheriff announce a key shift in the case. The major search effort, the largest in state history, would be scaled back. And something else.

UNIDENTIFIED SHERIFF: We are going to continue this investigation on a criminal level.

It was now a criminal matter for police, and it appeared that one of the people at the front and center of their investigation was one of the family members standing right behind them.

Coming up, the investigation takes a shocking turn.

KYLE IBOSHI: This was really the first time that investigators said, `We're looking at this woman. We want more information about her.'

When Little Boy Lost continues.

Part 4:

KATE SNOW: How long have you been in this house?

DESIREE YOUNG: Five years. Going on five years.

For Desiree Young, Kyron Horman's mother, happy memories and hope are what have kept her going during these endless, dark days of waiting for her little boy to come home.

KATE SNOW: When was that taken?

DESIREE YOUNG: That was at the beginning of the school year.

Desiree gave Dateline a tour of the home in southern Oregon that she and her husband, Tony, have made for her two boys, her older son and Kyron, who visited on weekends and holidays while living full time in Portland with his father, Kaine, and stepmother, Terri.

KATE SNOW: Did he lose his front tooth? Is that...

DESIREE YOUNG: Uh-huh. Yeah.

KATE SNOW: Did the Tooth Fairy come?

DESIREE YOUNG: Of course. Of course. He loves the Tooth Fairy.

And she showed us the bedroom: Bunk beds for the two boys, Kryon's Batman pillowcase on the lower bunk. She's left the bed unmade, the way Kyron left it the last time he was here.

DESIREE YOUNG: His bed, I still can't bring myself to make it. It's the same as it was when he last slept in it, and I can't put away his laundry. His cars are still out. He was playing with his little car wash the last time he was here.

Desiree is living with the agony of not knowing where her little boy is, a pain that grew more acute when, in the second week of the hunt for her son, authorities started calling whatever had happened to him a crime.

As part of the investigation's new focus, law enforcement distributed a flier asking people if they had seen Kyron the day he went missing – but the flier caught people's attention for another reason. It featured a picture of Kyron's stepmother, Terri Horman, and the white pickup she'd driven Kyron to school in that day, and even included the question, "Did you see Terri Horman at or near the school?"

KYLE IBOSHI: The release of this flier was really the first time that investigators pointed the finger at Terri Horman and said, `We're looking at this woman. We want more information about her.'

Authorities insisted the flier was only meant to jog memories about the day the little boy went missing and said Terri was not a person of interest or a suspect in Kyron's disappearance. But now many were wondering, `Just who is Terri Horman?'

KYLE IBOSHI: Everything that we have heard from her friends suggest that Terri Horman loved her stepson Kyron. She cared for him. She attended school events and was there to support him. We have also heard that she spent a lot of time caring for her 19-month-old daughter, Kiara, and Kiara was the apple of her eye, according to her friends.

Terri was a one-time teacher, now actively involved in her children's education, a fitness buff who won fourth place in a bodybuilding competition in 2005. But scratch the surface and a more complicated portrait of Terri Horman emerges: Five years ago she was convicted of drunk driving and pleaded guilty to reckless endangerment because her older son was in the car with her at the time.

And Kyron's mother, Desiree, has provided more details. There have been reports in the Portland press that Desiree and Terri were old friends, but Desiree insists that couldn't be further from the truth. She says she only learned of Terri in 2002, when Desiree, while eight months pregnant with Kyron, says she found out that Kaine had started a relationship with Terri.

DESIREE YOUNG: Unfortunately, Kaine was not faithful to me and met another woman.

KATE SNOW: That was Terri?

DESIREE YOUNG: Mm-hmm.

KATE SNOW: So all of the sudden you know that there's another woman. You're eight months pregnant.

DESIREE YOUNG: Yeah.

KATE SNOW: Must have been a low point in your life.

DESIREE YOUNG: Yeah. It was pretty hard to handle. I cried solid for two months and didn't leave the bedroom because I didn't understand why she somehow equated to something that was better than me and my son.

Kaine, however, insists that he and Desiree had broken up before he stated seeing Terri, agreeing to live separate lives under the same roof just until their baby came along. In any event, Kaine and Desiree eventually divorced. At first Desiree moved into a new place near Kaine's home in Portland. Little Kyron lived with her for the first two years of his life. But Desiree was sick with severe kidney problems.

DESIREE YOUNG: I had gotten to the point where I was in the hospital usually

three or four times throughout the year.

KATE SNOW: Your kidneys were failing?

DESIREE YOUNG: Yeah. I was so sick that I was passing out at times.

Desiree says she went to Canada for treatment and gave Kaine temporary custody of Kyron. When she got back, still recovering and drowning in medical bills, they decided together that Kyron would be best off staying with his dad. She admits that, despite the anguish Terri had caused her in he past, she now thought Kaine and Terri could give Kyron a good life.

DESIREE YOUNG: I didn't see anything that I was unhappy with. I didn't think that my child was unhappy.

But in hindsight, she regrets the decision.

DESIREE YOUNG: I have to say honestly I've regretted it for a very long time. I don't sleep at night because of it.

By the third week into the investigation of Kyron's disappearance, Desiree's guilt was morphing into fear and dread. While her suspicions about Terri Horman were rising each day, local press was now reporting that Terri Horman was asked to take a second polygraph test.

Instead of talking about Kyron, the public's focus was shifting to Terri.

MEREDITH VIEIRA: The fact that she's had two polygraph tests, and although she is not considered a suspect...

On the TODAY show on Friday, June 25th, Desiree held her tongue, and Kaine defended his wife.

KAINE HORMAN: She, like the rest of us, is extremely committed to finding Kyron, and she's working extremely hard with investigators, as are the rest of us, to help bring him home.

But by that weekend, a bombshell landed in Kaine's lap, turning his world upside down and causing him to fear for his daughter's safety. According to Kaine, police informed him of something that prompted him to flee his home with his young daughter, Kiara. The next day, a

Saturday, more turmoil at the house, 911 calls from the home… By Monday, it was clear a catastrophic rift now divided Kyron's family. Terri was served with divorce papers, and a restraining order was obtained against her by her own husband. And did it have anything to do with Kyron's disappearance?

Coming up, for the first time Kaine opens up about a bombshell revelation from police about Terri.

KATE SNOW: You've been informed that she was trying to hire someone to murder you?

When Dateline continues.

Part 5:

It was late June, and a flurry of 911 calls, divorce papers and a restraining order begged the question: Something big had just gone down in the home of Kyron's father, Kaine, and stepmother, Terri. But what? Then, on July 4th, fireworks of more than one kind lit up Portland.

UNIDENTIFIED REPORTER #1: [newscast] A bombshell of an accusation in the Kyron Horman investigation.

Kaine says police informed him of a harrowing discovery. About six months before Kyron went missing, Kaine's wife, Terri, had allegedly tried to hire a landscaper to kill him. Kaine opened up to Dateline about the allegation.

KATE SNOW: You've been informed that she was trying to hire someone to murder you?

KAINE HORMAN: Mm-hmm. I didn't believe it at first. It was something that I couldn't even wrap my head around at the time. Just thought...

KATE SNOW: There had been no indication in your marriage –

KAINE HORMAN: No.

KATE SNOW: – that things were that bad or that she was upset with you?

KAINE HORMAN: No.

Kaine has said there were more ups and downs in his marriage to Terri after the birth of their daughter 20 months ago. Still, Kaine says he never saw something like this coming.

KAINE HORMAN: Nothing so far one way or the other that would have even put that on my radar screen as something to worry about.

It was a pivotal moment for Kaine, the moment he stopped trusting his own wife, the woman who'd been helping raise his children. Authorities are still investigating the alleged murder-for-hire attempt, but if the allegation against Terri is true, many think it speaks volume about the mission to find Kyron.

KATE SNOW: Do you think she is capable of hurting a child?

KAINE HORMAN: If you asked me before this situation, my answer's no. Based on what I know now, I don't know. I think anything is possible based on the way things have gone over the past few weeks.

KATE SNOW: You fear for your safety now, Kaine? For your daughter?

KAINE HORMAN: I fear for my daughter.

While Kaine doesn't say why Terri or anyone else might want to harm him or Kyron, the shocking allegation that his wife had tried to have him killed caused a dramatic shift in his thinking. Reeling from the news, he now believes Terri is somehow involved in Kyron's disappearance.

KATE SNOW: Do you think that Terri has more information than she's told investigators so far?

KAINE HORMAN: Yes.

KATE SNOW: About where Kyron is?

KAINE HORMAN: Yes.

KATE SNOW: And so your message to her now is what, Kaine?

KAINE HORMAN: Fully cooperate with law enforcement. Tell the truth.

Desiree and Tony also say the alleged murder-for-hire plot was a turning point for them, the point when they went from being suspicious to being convinced.

TONY YOUNG: When I heard that, that made the decision in my mind. At the fork in the road, we knew which road to go down.

It was enough for Desiree to finally say in public what she had been thinking in private for weeks.

DESIREE YOUNG: We implore Terri Horman to fully cooperate with the investigators to bring Kyron home.

Now Desiree wonders not only where her son is, but also what she could have done to spare him this nightmare. The thought gnaws at her: She wasn't there when Kyron needed her most.

KATE SNOW: What keeps you up at night?

DESIREE YOUNG: To know that I was four and a half hours away when he needed me to protect him, that's what I feel guilty for. The fact that I had to work that day instead of going to the science fair like I wanted to, that I feel guilty for, too.

Looking back, she blames herself for missing signs, says she had a mother's hunch that something wasn't right for Kyron in the months before he disappeared.

DESIREE YOUNG: He wanted to come live with us. He expressed that on several occasions. And just several times he would just break down and just sob because he wanted to stay.

Kaine, Kyron's father, says he didn't see a change in Kyron, but Desiree wonders if she should have acted on her gut feeling, because she and Tony now believe not only that Terri was involved in Kyron's disappearance, but that it had been in the works for a while.

TONY YOUNG: I absolutely believe that Terri Horman is responsible for Kyron's disappearance.

DESIREE YOUNG: And I do, too.

KATE SNOW: With help? Did someone help her?

DESIREE YOUNG: We don't have any evidence that indicates that, but we personally think that's the case.

KATE SNOW: Do you think Terri Horman planned to do something?

DESIREE YOUNG: Something with Kyron?

KATE SNOW: To Kyron?

DESIREE YOUNG: Oh, yeah, without a doubt.

Again, Terri Horman has not been charged with any crime, hasn't even been named a person of interest by investigators, though she has hired a heavy-hitter defense attorney, Stephen Houze. Terri herself has been staying out of sight and silent, but that hasn't stopped a seemingly endless flow of personal details about her life. While the world's been out looking for Kyron, allegedly, his stepmother has been busy with other things.

KYLE IBOSHI: Dozens of e-mails, including graphic photographs of sexual activity…

Coming up, troubling allegations of an affair and growing concerns. Could another child be in danger?

KATE SNOW: You think she came here with the intention of finding her daughter and taking her?

When Little Boy Lost continues.

Part 6:

Kyron's father had moved out of the home that he shared with his wife and Kyron's stepmother, Terri Horman, stating in court documents that he believes she had something to do with Kyron's disappearance. Where once there were four parents standing together, now it was three against one. The seven-year-old was still missing, but with each passing day the drama swirling around the little boy's family almost obscured that grim fact.

In the weeks since Kyron disappeared, Terri may have stayed away from the cameras, but, according to court documents, she certainly wasn't idle. Just a few days after Kaine moved out with his daughter Kiara, Terri went to this gym where Kaine is a member. Owner Bob Briede told Dateline about her visit.

BOB BRIEDE: Terri was inquiring if Kaine was here working out, and then she asked if her daughter was here in our kids' club, and the comment she made: `Well, if she had been here, I would have taken her.'

KATE SNOW: You think she came here to the club with the intention of finding Kiara, her daughter, and taking her?

BOB BRIEDE: That's certainly what it looked like.

The gym owner says he was so alarmed, he called police – but even if Terri was really just a distraught mother pining for the daughter she'd been separated from, talk of taking a child mystified Kyron's mother, Desiree.

KATE SNOW: Hearing that, what do you think?

DESIREE YOUNG: She's got some guts, I'll give her that. Now's not a good time to be doing stuff like that, but I guess I don't expect anything less.

And then a revelation about what Terri Horman has allegedly been up to since Kyron went missing that truly tipped this story into the realm of the bizarre. It involves this man, Michael Cook.

Cook is an old high school friend of Kaine's. They recently reconnected. In the first days of the hunt for Kyron, Cook joined the search... and seemed to go out of his way to defend Terri when suspicions about her first emerged.

MICHAEL COOK: I would hope that if people had energy they would put it toward helping to find this missing boy, as opposed to investigating and speculating about whether the family did or didn't have something to do with it.

But now, court documents filed by Kaine's attorney allege that Michael Cook got involved in more ways than one. NBC affiliate KGW's Kyle Iboshi:

KYLE IBOSHI: Come to find out, according to the court documents, that Michael Cook was having an affair with Terri Horman three weeks after Kyron disappeared.

The court papers allege Terri and Michael Cook exchanged sexually explicit text messages and pictures. Cook has admitted to KGW that he sexted with Terri, but denied having sex with her. And the real issue for many has become – if those allegations are true, what was Terri Horman thinking?

KATE SNOW: When you heard there were these new court documents and they say that she developed this relationship with this man, that they were sexting, texting each other—you roll your eyes.

DESIREE YOUNG: Yeah, I'm sorry. I guess, to say it tactfully, it goes to someone's character if you're doing something like that. I mean, it's disgusting.

Now to the latest legal fallout. The restraining order against Terri gives Kaine temporary custody of their daughter Kiara. Terri is not allowed to see her daughter. The court also ordered Terri to move out of the family home. Kaine has moved back in.

KAINE HORMAN: He's not there with us, so it's still—it's still pretty empty.

And if this continuing scuffle in the family court looks like a sideshow to some, others see it as a calculated tactic drummed up in part by law enforcement: Isolate Terri Horman and maybe she'll talk.

KYLE IBOSHI: They've been slowly applying the pressure throughout this entire investigation, alienating her from her friends and family. Terri Horman is here by herself. The rest of the family is over here. They want Terri Horman to feel alone and potentially be cooperative in some way.

And just days ago, authorities appeared to be zeroing in on Terri Horman's shrinking inner circle. Police reportedly executed search warrants on the homes of some of Terri's friends. Kyron's family released a statement saying police told them that one of the friends, DeDe Spicher, has been in close communication with Terri and has been providing Terri with support and advice not in Kyron's best interest. Spicher's lawyer says he doesn't know what they're talking about and she had nothing to do with Kyron's disappearance.

Just today, Spicher was spotted emerging from a courthouse, where her attorney said she had been called before a grand jury.

UNIDENTIFIED MAN #6: My understanding is just to solicit information.

Spicher has not commented publicly, and police have not labeled her or anyone else a person of interest or a suspect in the case. In family court recently, Terri Horman's attorney, Stephen Houze, called the speculation surrounding Terri a witch hunt and said she's received threats. Dateline asked Terri and her attorney for an interview. Mr. Houze said in a letter to DATELINE it would be a "violation of clear ethical standards" for him to respond. He wrote, "There are matters currently pending before an Oregon court concerning Ms. Horman. No party or attorney may make public comments intended to influence the outcome of a matter pending before a court."

And Kaine Horman is for now done talking about his soon-to-be ex-wife.

KAINE HORMAN: I'm here for Kyron today. I don't really want to talk about Terri.

He and the rest of the family want the public to remember there is still a little boy missing, messages of hope still trickling in. This one from a child says, "Dear Kyron, I hope your parents find you soon."

KAINE HORMAN: He's still out there. He's still out there. We just need to find him.

On this, Kaine, Tony and Desiree remain more united than ever. They believe Kyron is out there, somewhere, alive. Just moments before our interview, his mother sketched out this message, directly to whomever is holding Kyron.

DESIREE YOUNG: [reading] ‘To the person or persons that have Kyron, I miss my son so much that I can't breathe at times. My heart aches every second of every day, and I am afraid that I can't live without him. I know that this situation has turned out much bigger than anyone could have ever imagined. Please do the right thing here and help us find him. Think about Kyron. He needs me as well. There are so many things he hasn't gotten to do yet. Please let him go. Just take him to a remote pay phone and tell him to call 911, and then we can come and get him.’

KATE SNOW: Millions of people have seen his photo.

DESIREE YOUNG: Yeah.

KATE SNOW: Do you wonder why someone hasn't said something yet?

DESIREE YOUNG: I do. I do wonder that every day. I pray for them to come forward and have the strength...to do what's right for Kyron.

ANN CURRY: And if you have any information regarding Kyron Horman's disappearance and would like to contact a tip hotline, go to our Web site at dateline.msnbc.com [see above]. And that's all for this edition of Dateline Monday. We're back again for DATELINE Friday at 9/8 Central. I'm Ann Curry, and, for all of us here at NBC News, good night.

More links

Read Kate Snow's blog about covering the investigation: "The stories that stick with me forever are the stories that touch me as a parent."
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