Transcript for Woman Dies After Being Thrown Into River While Fishing With Husband: Part 1
Reporter: On a boat, on a river, a man and a woman, husband and wife. Gone fishing, that's the story. But night is coming and one of them is about to lose their life. So we're getting close here? Yeah, we're getting close. This is about a mile from it. Reporter: Before this mystery ends there will be three missing women, all last seen alive with the most unlucky of husbands. Three lost women. Forgotten but for a fearless private eye in Texas. I'm a hands-on girl. Reporter: With a burr under her saddle and recorder in her bra. You've had a lot of women. Reporter: A relentless reporter from Mississippi. This is my lair. This is where I work on my computer and work on cold cases. Reporter: And a grieving mother who got a crazy idea and just could not let it go. It just feels like this is my duty to make this happen. The very first thing she asked me was, would you be interested in writing about a serial killer living in Mississippi and I was kind of like, "Yeah." Reporter: Lake Charles, Louisiana, down by the gulf of Mexico. Cajun country, Spanish moss, and long-legged egrets. A tale tangled as old fishing line. Best unraveled by boat. Cruising through a ship graveyard. It's right up here on the right. Reporter: Our guide, investigative reporter jerry Mitchell, he's already had a long career uncovering old testament evil in the deep south. Stories like the Mississippi burning murders that led to the conviction of klansmen. There it is. This is it. Okay, this is where it is. Reporter: His latest work appear in the usa today network documentary series called "Gone." The case of Mary Horton Vail, haunting the Louisiana delta since 1962. ? I can't stop loving you ? Reporter: On the radio, ray Charles "Can't stop loving you." In the white house, president Kennedy on the brink of the Cuban missile crisis. And soaring somewhere high overhead, John Glenn, the first American in orbit. Back on Earth, in Lake Charles, Mary Horton and Felix Vail have only just begun living the life, all smiles in home movies. The dashing Felix sporting a fedora just a few months before it all went bad. Mary had been the high school homecoming queen in Eunice, Louisiana, tiaras and parades. Her home movies reveal a real looker with southern charm. One of her biggest admirers, Mary's little brother will Horton. Mary was one of those people, when she walked into the room, she made everybody feel good. She was kind of this larger-than-life girl that everybody loved. She was a beauty for sure, yes. Reporter: Classmates and sorority sisters remember college days at Mcneese state with Mary like it was yesterday. Not only pretty on the outside but pretty on the inside. People really were drawn to her. Reporter: Felix works in a chemical plant, and he has plenty of chemistry after work too. Very nice-looking man. She just kind of fell in love from the get-go. I had one woman tell me that Felix Vail looked like he'd been kissed by heaven. He had this charismatic aura. Reporter: Funny thing about Felix, though. I think Felix was the bad boy. Reporter: Mary's friends say they didn't like him much. Can't remember why. For some reason we didn't care for him. I do remember that. Reporter: Now in the fall of '62, after a year of marriage, Mary and Felix have a baby, Billy, and some unexpected good news. Reporter: And they thought, or she thought she was pregnant again? She did. She thought she was pregnant again, told her friends she thought she was pregnant. Reporter: Were they happy at the beginning, do you think? Oh, absolutely. The family was beginning to start, you know? Reporter: But behind those backyard smiles, something dark. One of her sorority sisters remembers a mysterious premonition. I remember in the dorm that Mary had always told us she was going to die young by drowning. I never forgot that. Reporter: One Sunday evening, Felix gets the notion to take Mary fishing out on the river they stay out late past dark. Something until this day, her brother says, he can't figure out. Reporter: Can you tell me a little bit about the fear of the water? She could go in a swimming pool. She was fine as long as she could see the bottom. Reporter: You call that dark water down here, right? Dark water. Reporter: And that means you can't see the, see through it. And yet there's Mary. You can see her in your mind's eye. All those years ago dutifully cruising up that corkscrew of a river with Felix. Then Mary's fear comes tragically true. Felix describes a freak accident. He says Mary spots a stump in the water, he swerves to miss it, throwing her into the river. She saw a stump, said something, he whipped the boat, she fell out. That's -- that was his story. And then he dove in the water and tried to save her, and couldn't save her. Reporter: The young mother, so lively and loved, taken by the river, vanishing in the dark water of the Louisiana delta. Gone.
This transcript has been automatically generated and may not be 100% accurate.