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Watch the Dateline episode "Wreckage" now

Josh Mankiewicz reports.

Our story begins with 22-year-old Molly Matheson.

In 2017, Molly was working part-time at a lingerie store in Fort Worth, Texas, where she was the model employee.

But on Monday, April 10, 2017, Molly Matheson was late for work. A couple of hours into Molly’s shift, her boss began to worry. This wasn’t like Molly at all.

So she called Molly’s emergency contact. Her mother, Tracy, answered the phone.

Tracy quickly drove to Molly’s apartment, already feeling frantic.

And when she entered Molly’s bathroom, she found her daughter on the floor of the shower.

Molly was crumpled over, not moving.

Tracy called for an ambulance.

But it was too late, Molly was dead.

Police responded to the scene and began to investigate.

The apartment looked undisturbed, and nothing appeared to be missing. There was no indication of a struggle.

The responding officer decided to call in the homicide detectives.

It was clear Molly had been murdered.

Loved ones remember Molly as outgoing and carefree.

Investigators soon had a suspect in mind. They just needed DNA results to come back so they could make an arrest.

But five days later, on Friday, April 14, 2017, another woman, 36-year-old Megan Getrum, went for an after-work hike in Plano, Texas.

On Sunday, she didn’t show up for her brother’s birthday party.

And on Monday, Megan missed work.

Megan’s brother decided to call the police to report her missing.

The Plano Police Department got the case and began the search for Megan.

They brought in search teams, canines, and helicopters, but there was no sign of Megan.

That week, about 20 miles from Plano, the homicide unit in Dallas found the body of an unidentified woman in a lake.

It was Megan. She had been murdered.

Her family was devastated.

Loved ones remember Megan as a cat lover and a talented artist and photographer.

Detectives soon came to believe Molly and Megan’s cases were related.

And they learned their suspect had a history.

Multiple women had accused him of rape.

And if someone had listened to them then, Molly and Megan would probably be here now.

Watch the full episode, “Wreckage” now.

You can also watch on Peacock TV or listen to the podcast.

After watching the episode, you can read the full statement from the Allen Police Department about their investigation.

Learn about Project Beloved: The Molly Jane Mission -- the non-profit Tracy Matheson created in honor of her daughter to empower and advocate for sexual assault survivors.