Produced by Lourdes Aguiar, Alec Sirken, Jenna Jackson and Chris O'Connell

[This story originally aired on Oct. 22, 2011. It was updated on July 7, 2012.]

Since the 1970s, over 30 young women and girls have disappeared or been found murdered in the 50-mile desolate area between Houston and Galveston - a stretch of land that some call a highway of hell.

"This bridge up ahead had a sign on it when you came out in this direction...it said, 'You are now entering the cruel world,'" federal agent Don Ferrarone pointed out as he drove along Interstate 45 with "48 Hours Mystery" correspondent Erin Moriarty. "And it's just, you know, it's just a perfect place [for] killing somebody and getting away with it."

"If you can just imagine having one of these little girls out here...one of these young girls out here...and there's no chance for them to be rescued, to be helped. And they're on they're own," said Ferrarone.

It was the haunting faces of the lost that inspired Ferrarone to write the screenplay for the movie "Texas Killing Fields."

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It's also what compelled "Avatar" star Sam Worthington to take part.

"I looked at that and it was just tens and tens of girls that had gone missing and I have got a young sister and you know it kind of disturbed me in a way that I just said straight away, 'I wanted to be a part of this,' to get this story out and make people aware of what's gone down there will hopefully maybe shed some light on some of the disappearances and the mysteries involved," he said.

The movie was released ibn 2011, but while the mystery of the fields may be new to Hollywood, it has consumed the lives of many Texas cops for over the last four decades, including investigators Brian Goetschius and Michael Land from Texas City.

Land served as a model for Sam Worthington's rough-and-tumble character in the film.

"There's a scene where your character goes in and ends up in a brawl right inside that bar," Moriarty noted to Land. "Ever happen to you?"

"Oh, hundreds of times," he replied.

"I hear you guys also described as angels, but kind of different angels. How do you see yourself?"

"Warrior angel...they're the biggest, baddest angel," he replied. Land even sports the symbolic warrior tattoo on his arm.

The other lead character in the film, played by Jeffrey Dean Morgan of "Gray's Anatomy," was inspired by the more genteel Brian Goetschius.

Asked what kind of angel is Goetschius, Land called him "the guardian angel...He's Mr. Helper, he's gonna help everybody."

In the film, Goetschius' character prays over bodies. Goetschius does that in real life, too.

"Are you praying for their souls?" Moriarty asked.

"Oh sure. For me it's that little bit of comfort to step into it and give people some answers," he replied.

"But isn't it hard to keep your faith when there's so much evil, and that's what you see here? These cases involve pure evil."

"I've never stopped long enough to -- to realize that. I just keep going, and -- and the faith is there.

Twenty-five years after the string of murders began, Goetschius became yet another cop to face the darkness. In March 1996, 13-year-old Krystal Baker suddenly vanished from the gritty industrial town of Texas City.

"I realized, at that point, that the devil was there," he said.

And true to form, Goetschius became a guardian angel for Krystal's mom, Jeanie Baker.

"And I love guardian angels and this one here reminds me of Krystal," she said, pointing to an angel at a shrine in her home.

Baker is still haunted by memories of her daughter.

"I dream about her mostly when she was a little girl. And every once in a while when she's a teenager," she explained. "And she told me one time, she says, 'Mama, I'm just out here hangin' out with my friends. Everything OK.'" And I woke up the next day. I wished I could have stayed in that dream a little longer," she continued in tears.

Krystal was striking, says Baker, and resembled a great aunt -- Norma Jean Baker -- who became larger-than-life movie star Marilyn Monroe.

"Whenever anybody mentions Krystal Baker, they always say she looks or looked a little like Marilyn Monroe," Moriarty noted.

"Yeah, well, she does," Baker replied. "She's kin to her from -- her dad's side of the family."

"And she had a heart of gold, but she was a typical teenager, you know? She was 13, goin' on 14," said Baker

But like any teenager, Baker says Krystal had a rebellious streak and on March 5, 1996, Krystal had an argument with her grandmother and stormed off.

Krystal called her mom from a nearby convenience store.

"I said, 'You need to go back to your grandma's house and stay there.' And then she walked out," Baker said. Krystal vanished.

Frantic, Baker called the Texas City Police Department for help, but she was in for a rude awakening.

"So, the police didn't help you look for your daughter?" Moriarty asked.

"No, they really didn't. They just-- kept telling me she was a runaway," she said. "So, for that to happen and -- and have -- be helpless, nobody helping you was really rough."

Brian Goetschius admits that missing kids -- particularly teenagers -- were handled differently in those days.

"When she first disappeared, did the police take it seriously? Moriarty asked.

"It was under the radar," he replied. "It -- it was -- a runaway, a missing person. And -- and not that we didn't take it serious, but it -- it was the way it was. I mean we entered it in the computer as a runaway and you know, went about your business."

That is until two weeks later.

"One day, I was getting ready for work and Goetschius called me and told me that there were some pictures I needed to come down there and see," said Baker.

Krystal had been beaten, sexually assaulted and strangled. Her body was then dumped under an interstate bridge two hours away near the Louisiana border.

As it turns out, Krystal's body had actually been found the very same day she went missing, but in a different county. She was listed as a Jane Doe for two weeks... her killer unknown.

"So, for those two weeks that I was lookin' for her, she was already dead," said Baker.

"What made the Krystal Baker case so difficult to solve? You found her body," Moriarty noted to Goetschius.

"We had a two-week window that we lost," he explained. "I mean, people can't remember who they saw at a convenience store two week ago, walking down the road, hitchhiking. It -- it just wasn't there."

Krystal's case soon grew cold. Her story was mostly unknown to the public until a year later when another little girl disappeared.

"I was thinking it was the same person that did it to my daughter," said Baker.

Just half an hour away in suburban Friendswood, 12-year-old Laura Smither was abducted while jogging on her street.

"Was that when people really started saying, "Oh my gosh," Moriarty asked.

"And it was so unusual for over there that -- that this couldn't happen in my neighborhood," Goetschius replied. "And-- and lo and behold, that monster is there. We know he was."