Mary Virginia Carpenter was a hopeful and driven young woman, despite the many setbacks life had already thrown her way.

She had medical difficulties as a child, including a hip infection that crippled her for a time. The infection and subsequent surgeries resulted in the permanent shortening of one leg and a life-long limp.

Her father died when she was young, and her mother became very ill, making Mary put her life on hold to care for her. All this led Mary to an interest in the medical field, and the desire to attend Texas State College For Women, now known as Texas Women's University in Denton, Texas.

Mary made it to Denton but never got to enroll. She's been missing for 75 years, making her Texas' oldest unsolved cold case. 

So what could have happened to Mary? We'll take a look at the circumstances of her disappearance, and some theories about what happened to her.

June 1, 1948, was the last day Mary was ever seen. Mary took a train from her hometown of Texarkana, Texas to Denton. On the train, she struck up an acquaintance with a middle-aged woman named Marjorie Webster.

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Marjorie and Mary took a cab from the train station to the college campus, but Mary realized that she failed to check on her bag. She took the same cab back to the station, where she signed a claim check with a railroad employee, as her bag had not yet made it in.

The cabbie, Edgar Ray "Zack" Zachary, agreed to go back to the station in the morning to retrieve her bag and drop it off at Mary's college campus for her. Zachary claimed he dropped Mary off on campus at 9:30 p.m. He said that he saw Mary talk to two men in a pale-colored convertible and that she seemed to "know" them.

That was the last time anyone saw Mary Carpenter

But no one missed her immediately. On June 4th, Mary's boyfriend Kenny Branham called Mary's mother to tell her that he could not get ahold of Mary. Mary's mother alerted the police and then drove to Denton in the middle of the night to look for her daughter.

The cab driver Zachary was a natural suspect since he was the last person to see her alive. His wife told police that he was home by 10 p.m. that night. Zachary had dropped Mary's luggage off at the college when he said he would, but strangely, he left it on the lawn where it sat for two days before anyone noticed it. Everyone else delivered luggage directly to the rooms of the people to which they belonged.

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Despite a massive manhunt and a huge reward for anyone who helped find Mary, she was simply never found. People claimed to spot her, or the pale-colored convertible, but no leads ever led anywhere. A body was found, with one leg shorter than the other, but the dental records didn't match.

Mary was declared legally dead in 1955, as per Texas law. Mary's mother never stopped looking for her, even if her only hope was to recover Mary's body.

It was later revealed that cab driver Zachary's wife had lied to police- he had not gotten home until 2 or 3 a.m. He had beaten two polygraphs, but we now know that polygraphs are junk science, easy to beat by calm liars and sociopaths. In 1957, Zachary was charged with an unrelated attempted sexual assault.

So do we like Zachary as our killer? Perhaps. But if he had dumped Mary's body in any obvious place like a drainage ditch, it was never found. Perhaps he could have weighed her down into Lewisville Lake, which is too deep to drag.

Maybe Mary simply ran off, but this seems unlikely for a girl with nothing to hide and a deep devotion to her mother. Perhaps she was killed by those two familiar men in the convertible if they actually existed.

Another possibility is that she was murdered by a serial killer: The Phantom Killer of Texarkana, as Mary was acquainted with three of his victims. However, The Phantom Killer targeted couples in cars, and instead of perfectly covering his tracks, he left a huge mess each time.

We will likely never know what happened to poor Mary that June night, but perhaps there's hope that maybe someday someone will discover a vital clue that can finally bring closure to this 75-year-old case.