 24 years after this girl vanished on Thanksgiving, her brother made a disturbing confession. In a police interview room in Florida, David Lambert labors over a confession. He's there because his sister disappeared more than 24 years ago, and officers are trying to close the case. But does David know more about the mystery than he has been letting on? Well, as investigators are about to find out. The 38-year-old does indeed have a secret that he feels compelled to share, and it's a disturbing one, to say the least. The story begins on November 27, 1985. Back then, David and his sister Martha Jean lived with their parents, Howard and Margaret, in St. Augustine, a city on the northeastern coast of Florida. As was the case with many of their neighbors, the Lambert's dwelling was a trailer found in a semi-rural area a few miles away from popular beaches. At that time, David was 14, while Martha Jean was 12. The younger sibling was a seventh grader at the city's Keterlinus Junior High School, and was of small stature, weighing only 70 pounds. However, according to David, Martha Jean had a combative nature that made her a force to be reckoned with despite her slender frame. On that day in November 1985, the Lamberts were getting ready to celebrate Thanksgiving. Unfortunately, though, they burned the turkey, and Howard reacted with anger. So, eager to escape their father's shouting, David and Martha Jean left the trailer. And as they wandered around their neighborhood, David gave his little sister some money to spend in a local store. Then, while on their travels, David and Martha Jean arrived at the defunct Florida Memorial College, which by that point had already been abandoned for several years. But even though the college was scattered with rubble and shards of glass, it was a popular place for local children to play at. In fact, in a 2010 interview with the St. Augustine record, one detective would even describe the surroundings as like a poor kid's Disney world. Sadly, however, David and Martha Jean's adventure was about to take a tragic turn. According to David, his sister had decided to leave the abandoned college and go somewhere else to play. After that, she simply vanished. And even though police subsequently launched an investigation into Martha Jean's whereabouts, no trace of the girl was found. Several attempts were made to get to the bottom of Martha Jean's disappearance over the following years. Right from the start of the investigation, though, detectives had suspected that David might know more than he was letting on. Still, without any clear evidence to prove that a crime had been committed, law enforcement were unable to take action against Martha Jean's brother. Meanwhile, life in St. Augustine moved on. Devastated by their daughter's disappearance, Margaret and Howard went their separate ways. Then, in 2000, David found himself in trouble with the police after allegedly attempting to write a bad check. And when they picked him up, he reportedly made a bizarre confession. In fact, in a 2010 interview with the Florida Times Union, St. John's County Detective Sean Tice revealed that David had claimed to know what had happened to Martha Jean. I need to get this off my chest, David is reported to have said. I'm responsible for my sister's death. Apparently, he went on to confess that he had buried Martha Jean in a local Kokina mine. But when police arrived at the mine to investigate the claim, they could find no trace of Martha Jean's remains. And in the absence of this vital evidence, no charges were brought against David. Then, in June 2010, Tice and another detective, Howard Cole III, made a final attempt to solve the most enduring missing person case that the county had ever known. Initially, Tice and Cole began their investigation by interviewing friends, family members and neighbors who had lived near the Lamberts at the time of Martha Jean's disappearance. And, interestingly, a number of them suggested that the officers should take a closer look at David's story. As a result, in August 2010 Tice and Cole brought David into the interview room. And over the course of three sessions, David, now in his 30s, gradually confessed to his role in his sister's disappearance. Apparently, on that fateful day in 1985, Martha Jean had asked him for more money when they arrived at Florida Memorial College. Her sibling, however, had refused that request. According to David, the belligerent Martha had then lashed out and hit her brother, at which point he pushed her away in retaliation. But the slight girl reportedly fell over backwards as a result of that shove, hitting her head on a piece of metal jutting out from the ground. Apparently, the metal pierced her skull, causing a fatal injury. And so, however indirectly, David believed that he had been the cause of his sister's death. Tice's report, meanwhile, would reveal that David said he had tried to help the girl at first. Dee, Lambert stated when he lifted Martha up, that, there was a large hole in the back of her head and blood was pouring out, he wrote. Dee, Lambert stated he initially called out for help, hoping that someone would be walking by and hear his cries. But when no one came, David is said to have taken matters into his own hands. Allegedly, he used a broken road sign as a shovel to dig a makeshift grave. And when the detectives asked David why he had not told his parents the truth, he explained that he had been scared of their reaction. In fact, Tice believes that David was living in fear of his mother Margaret, a situation that apparently remained the case at the time of the man's confession. He was terrified of his mama, Tice wrote. Still is. Eventually, spurred on by a photograph of Martha Jean that Tice had placed on the table, David wrote and signed a statement. And in it, he finally admitted his role in his sister's death. But that wasn't all, as alongside the written statement David also drew a map for investigators. Identifying the plot upon which the Florida Memorial College stood, it allegedly showed where Martha Jean was buried. A team was then duly sent out to investigate the location. But even though trained police dogs reacted to a certain spot, the crew were unable to locate a body. However, Margaret has not been as easy to convince of David's involvement in the case. Indeed, according to the mother, her son has been known to invent stories in order to get attention. As a result, she does not believe his confession. Instead, she is convinced that her daughter was kidnapped. Adding to the confusion, David himself later withdrew his statement, claiming that he had only told the officers what he believed they wanted to hear. But despite Margaret's protests, the investigation into Martha Jean's disappearance has been closed. And even though police believe David to be guilty, Martha Jean's brother will not be facing any charges. As a 2010 press release from the St. John's County Sheriff's Office revealed changes in the law since 1985, statute of limitations, the suspect's age at the time and other mitigating circumstances would preclude charges from being filed.