It's called the "Highway to Hell," a scary 50-mile stretch between Houston and Galveston, Texas, littered with mystery and misery. It cuts through a mix of murky swamps, old farms and abandoned oil fields, making it the perfect dumping ground for dead bodies.

Thirty women have disappeared along this lonely highway, some found in shallow graves near a place locals call the "Texas Killing Field." They are mostly young, pretty and brunette.

For years police have wondered if it's the work of one sadistic serial killer, or a handful of evil copycats. And now they are finally about to get some answers.

Jan Bynum keeps a yellow ribbon in the front yard of her home in Farmers Branch, Texas. Her daughter Kelli Ann Cox, a young single mom, is one of the missing.

Kelli spent her mornings studying at the University of North Texas, and the rest of her days being mom to her young daughter Alexis.

On July 15, 1997, Kelli dropped 19-month-old Alexis at a babysitter's, then drove to Denton County Jail for a field trip with her criminology class. Her professor told the students not to bring phones, keys or personal items to the prison.

According to Kelli's boyfriend Lawrence Harris III, he and Kelli had a spare key made. They tested it the night before the tour to make sure it worked and then hid the little magnetic box in the wheel well of her vehicle.

After the tour Kelli heads back to her car. That's when Denton Police Officer Shane Kizer says the story takes a bizarre turn.

"She would have walked down the sidewalk on the south end of the building and come to this parking lot that's behind us where her car was parked at the time," said Kizer. "She was unable to get into her car at the time, unable to get it unlocked."

That spare car key that had worked just hours before now mysteriously would not open Kelli's car.

"She ended up coming back across the street," said Kizer. "She came to this business here which at the time was Rick's Drive-In. She went in, got change, came back out and used the payphone."

Kelli calls her boyfriend Lawrence for help.

Lawrence claims he drives straight to the jail, and when he arrives 35 minutes later, Kelli's car was in the parking lot, but she was nowhere to be found.

By 5:30 that afternoon Kelli's mom's heart was pounding.

"I knew absolutely without a doubt that there's something wrong 'cause that's when she had to pick Alexis up at babysitter," said Jan.

Police begin questioning those closest to Kelli. Everyone had an alibi, so police start with her boyfriend Lawrence. Lawrence passes four polygraph tests, and police eliminate him as a suspect.

Now, with no leads, no witnesses, no surveillance video, the case goes cold.

Then a possible break: Cops get a tip that William Reece, a convicted sex offender, had just been released from prison. A credit-card receipt from a gas station put the trucker in Denton the day Kelli Cox disappeared. But the hot tip quickly went cold when no evidence of her fingerprints was found in his truck.

Then, finally, this February, almost 19 years after Kelli disappeared, police finally make that terrible call to Jan, and a familiar face comes back to haunt her.

"He said it is William Reece who we're looking at," said Jan.

Reece is serving 60 years in a Texas prison for kidnapping a woman. Now DNA has just linked him to another murder in Oklahoma. Reece's attorney, Anthony Osso, says his client doesn't want to face the death penalty, and offers to tell cops where he buried the bodies of two missing young women, Jessica Cain and Kelli Cox, if they agree not to execute him.

"You've had those times over 19 years where something seemed positive and then ends up leading to nothing, and so I think you're kind of let down," said Kizer. "So I think especially with our investigators, they went with a cautious but optimistic approach."

Reece leads investigators to an area not far from the "Highway to Hell," where they do find Jessica Cain's body. And then Reece takes police to an old farm nearby where he says he buried Kelli Cox. In a shallow grave they find Kelli.

"They came back with the dental and said It's Kelli. There's no doubt it's Kelli," said Jan Bynum.

"I can be comforted that I know she's in God's arms," said Jan. "And I know that she's not in harm's way every minute of every day. And I can bring her home and put her to rest the way I want to."

Jan and her husband Nyles later adopted Alexis. The cute toddler Kelli left behind is now a young woman following in her mom's steps as a student at the University of North Texas.

As for that yellow ribbon, Jan is keeping it upm hoping the other girls out there in the Texas fields make it home too.

"I miss her a lot," said Jan. "I also know I was blessed with 20 years with her, and thank God for that. I know there are parents that only get to have their children for a few years. I got to have her for 20."

Sadly the pain that she feels could have and should have been avoided: William Reece was supposed to be sitting in prison the day that Kelli went missing, sentenced to 25 years for a rape conviction. However, because of a technicality, he only served nine years and was set free.