Inside the Mystery of Girl Who Vanished from Her Mom’s Home — Then Reappeared 700 Miles Away, 22 Years Later

A new episode from ID’s true crime The Curious Case Of… series premiering on Monday, Jan. 20, will look into one of the strangest missing persons cases some detectives say they’ve ever seen.

The new episode, titled “The Curious Case Of… The Girl Who Died Twice,” premieres Monday night at 10 p.m. ET on ID. The episode is focused on the decades-long search for Mary Louise Day, who went missing from her Seaside, Calif., home in 1981 when she was 13 years old and was believed by many to have been killed. But then, a woman with her driver’s license turned up in Phoenix decades later.

“Is this Mary Day or an imposter?” ID asks in the trailer for its new episode, which includes interviews with May’s sister Sherrie Calgaro and investigators who have long asked the same question.

Sherrie was 10 years old when her older sister Mary disappeared. Sherrie told 48 Hours in 2021 that she long had doubts that the woman who was stopped by Phoenix police in November 2003 and identified herself as Mary Louise Day was actually her sister.

Sherrie, Mary and their third sister Kathy grew up in an unstable home, bouncing from foster home to foster home throughout their childhood before returning to their birth mother Charlotte, who had married a military man named William Houle.

The Houles were stationed at Fort Ord along the California coast when Mary went missing in 1981. Investigators had a theory that William became angry and violent toward Mary the night she was last seen, believing the young girl had poisoned his dog, according to 48 Hours. The Houles began to act in a way that made authorities suspicious after Mary’s disappearance, detectives have claimed. (PEOPLE was not able to reach Charlotte or William Houle.)

“We’re not allowed to talk about Mary,” Sherrie recalled her sister Kathy telling her when she would ask what had happened, according to CBS News. Investigators dug up a portion of the backyard where the Houles lived when Mary went missing, according to 48 Hours, and cadaver dogs found a little girl’s shoe — but no body.

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Detectives told 48 Hours they traveled to Kansas, where the Houles later moved, to interview Charlotte and William about Mary’s disappearance decades earlier. According to detectives, the couple made statements that concerned them during that visit, 48 Hours reports. But then, seven months later, Mary suddenly reappeared in Phoenix.

“This case just gets weirder and weirder,” former Seaside Police Chief Steve Cercone told 48 Hours.

Things got even more confusing when detectives pressed the woman stopped by Phoenix police – dubbed internally as “Phoenix Mary” – for answers about who she really was and where she had been, if she was in fact Mary Louise Day.

Interrogations, DNA tests, and forensic photographic analysis eventually led investigators to the truth – one that Mary Louise Day’s sisters and detectives alike have still struggled to come to terms with.

New episodes of The Curious Case Of… air Monday nights at 10 p.m. ET on ID.