Lisa Davidson was just seven when her oldest sister Brenda disappeared.
She remembers very little of that day.
"My mom just told us that Brenda didn't come home from school," Lisa told Dateline. "I know they reported her missing, but nothing really happened after that."
It was March 4, 1974 when Brenda was last seen. She was four days away from her 14th birthday, and was the eldest of five siblings. The family had settled down in Woodbridge, Virginia. They attended church several times a week, and although they weren't on the higher side of the income level, they lived a pretty happy life.
But then Brenda went missing. Her sister Lisa told Dateline the family really didn't discuss her sister after that. It was too painful.
"I never had really seen my father cry. I wouldn't say we feared him, but we really respected him," Lisa said. "After Brenda disappeared, he came into church just sobbing. As a little kid, that really sticks with you, seeing your dad cry like that. The whole thing didn't bring us together -- it tore us apart."
The police of course were called, and a report was filed. But nothing seemed to come of it. And years began to pass with no answers.
When Lisa was in her early 20s, she began to grow more and more curious about the sister who disappeared all those years ago. She began to poke her mother for information about that day. With what information her mother remembered, she started to piece together the story and began to track down others who may have information.
What she discovered was several strings of rumors and theories, each the more puzzling than the next.
A woman at the local bus station in town told authorities she remembered a girl resembling Brenda purchasing a bus ticket the afternoon Brenda disappeared. But the woman couldn't recall the ticket's destination.
A story later emerged that the woman also told police she took the young girl to the bank with her before the girl was set to board the bus, as she was nervous about the girl being at the station all alone.
There is also a record of two classmates of Brenda's saying they walked her to the bus station that day. Lisa tracked the boys, both now adults. Both told her they didn't walk Brenda to the station that day.
Yet another story emerged from the gossip of teens in Brenda's class. A girl claimed she heard Brenda talking with two other girls about running away to Florida. Two of the girls reportedly did, but were later found and brought home, Lisa remembers. Brenda was not with them.
The number of stories that have emerged over the years is troubling to Lisa.
"It's like there is no solid information out there about my sister and what happened," she told Dateline. "A 14-year-old doesn't just survive on their own all these years. Even if she did run away, how did she get by alone? What if something horrible happened to her after?"
The decades that have passed haven't deterred Lisa. She's done searches of Brenda's social security number, in the hope perhaps she did runaway and started a life somewhere else. There was no activity.
She's submitted her DNA to various law enforcement agencies, in case Lisa's body sat as a Jane Doe somewhere. No matches yet.
She's reached out to the National Center for Missing and Exploited Children in an effort to get an age-progressed photo of her sister made. She thought maybe someone would recognize her and call in a tip. No leads have been developed yet.
Lisa is even now sending in her DNA to Ancestry.com on the small chance Brenda somehow had kids of her own, who themselves are looking for their family.
"You really never know," Lisa told Dateline. "I'm going to run down every avenue I can until we can find answers. She's my sister, of course I'm going to do everything I can."
Last year, Lisa was able to get the Prince William County Sheriff's Office to re-open Brenda's case as a cold case. It's unclear what leads authorities may have since uncovered, but it is a slight comfort to Lisa that Brenda's case is at least not just sitting in a box on a shelf somewhere.
Lisa's father passed away in 1985. Her mother died in 2015. Lisa and her other siblings have families of their own now. But something has been missing since Lisa was seven: her older sister Brenda.
"Having girls of my own now, I cannot imagine what my mother went through," Lisa told Dateline. "I just want answers and closure for our family. A part of our family is missing and we have to find it."
Anyone with information about Brenda's case is urged to call the Prince William County Sheriff's Office at (703) 792-6500. You can also visit the Facebook page set up by Brenda's sister Lisa at 'Find Brenda Sue Davidson' for more information.