FARMERS BRANCH -- The memories Alexis Bynum has of her mother come from photographs and stories told by relatives.

Those memories are particularly painful on this day.

Alexis was 19 months old when her mother, Kelli Cox, disappeared on July 15, 1997.

Since then, neither Alexis, Cox's parents nor any of her friends have heard from Cox, who was a 20-year-old honor student at the University of North Texas.

"I believe she was abducted," Alexis said during a recent interview. "I don't know if she's alive or not."

Though Cox has been legally declared presumed dead, Alexis and other relatives hang on to slivers of hope.

"I have always believed that she would walk through the front door one day," said Alexis, now 15 and a sophomore at R.L. Turner High School.

Cox's mother, Jan Bynum, said not knowing is the worst part.

"Hope can be good on some days, and hope can be painful," Bynum said.

Tour of jail

That July morning was like any other in the Bynums' home.

Before she left for work, Jan Bynum stopped by her daughter's room and said, "Have a good day. I love you. I'll talk to you this afternoon."

Cox drove from their Farmers Branch house to the Denton Municipal Complex in her beige 1989 Nissan 240-SX to meet up with her criminology class for a tour of the Denton Jail.

The brown-haired, blue-eyed senior followed her professor's instructions not to carry personal items into the jail, locking them up in her car and hiding a spare car key in a magnetic box under a fender.

When the tour was over, Cox discovered that her spare key didn't work and called her boyfriend, Lawrence Harris, to bring her another key.

She had to make the call from a Conoco gasoline station because she wasn't allowed to make a long-distance phone call from the police station. After calling, Cox bought a soft drink and headed back to her car about noon.

But when her boyfriend arrived, she was gone. Only her car was there.

Though hundreds of leads poured in to authorities in the weeks after her disappearance, no one has been arrested in a mystery that has stumped Denton police, the FBI and the Texas Rangers.

"We used every resource available at that time," said Denton County Sheriff Benny Parkey, who was the lead investigator on the case as a Denton detective. "As a police officer, you're hired to protect and serve, but once in a while you run across a case like this that just frustrates you."

Probable abduction

The theory that Cox left on her own accord was quickly shot down by authorities because it was clear that she loved her toddler daughter and was close to her parents. What's more, she had left all her personal belongings at her family's home in Farmers Branch, including $200. Also untouched was her bank account, which had about $1,000 in July 1997.

The conclusion: Cox was abducted.

Police established that she made the call to her boyfriend at 11:47 a.m., and he immediately left Farmers Branch for the 30-minute drive to Denton.

Harris, who had dated Cox for nine months, would later pass four polygraph tests to eliminate him as a suspect.

Authorities noted that Cox had a rose and the name "Francisco" tattooed on her right palm and a tattoo of a scorpion on her right shoulder.

"Francisco" was a former boyfriend, Francisco Almaguer, the father of her child.

He was in Dallas getting married when the disappearance occurred and was also eliminated as a suspect early in the investigation.

Other "people of interest" have surfaced from time to time, but leads have dwindled as the years wore on.

For Alexis

Immediately after Cox disappeared, Jan and Nyles Bynum took care of their granddaughter and in 2004 adopted her. Alexis calls them Mom and Dad.

Jan Bynum is vice president of human resources at Volunteers of America Texas in Euless, and Nyles Bynum, Cox's stepfather, is a retired jet engine inspector.

Jan Bynum says that a day doesn't go by that she doesn't shed a tear for her missing daughter.

"With a tragedy like this, I had two choices. I could have dug a hole and crawled in it," she said. "Or, I could move on for Alexis' sake, and that's what I did."

One of the most difficult days occurred in 2007, when Bynum went to a Denton County court to have her daughter legally declared as presumed dead, so Alexis could become the beneficiary and receive benefits from Cox's father -- and Bynum's ex-husband -- who had died.

Every missing-person story she hears stirs up the memories of her daughter's case.

The Elizabeth Smart and Jaycee Dugard cases have brought back painful memories for Jan Bynum. Dugard was abducted in 1991 and found alive 18 years later. At age 14, Smart was taken at knifepoint in June 2002 from her Salt Lake City home and found alive in March 2003.

And several reports of missing children in North Texas have prompted Bynum to volunteer her time to help those parents.

"I know what they are going through," Bynum said. "So I decided that if this could bring some good, I would help them."

Cold case

In March 2010, Denton Detective Eric Beckwith volunteered to take over the cold case because the previous detective had retired.

For weeks, Beckwith combed through mounds of paperwork on the Cox case and re-interviewed dozens of her relatives, friends and acquaintances. He researched the sex offenders and the violent criminals who were in the area that day.

"It was never a closed case, just inactive," Beckwith said.

But the Denton detective hasn't turned up anything new in the months that he has reviewed the case. A $25,000 reward remains for information leading to Cox's safe return.

"Somebody knows something about this case," Beckwith said. "Her family needs answers."

Domingo Ramirez Jr., 817-390-7763