In 1981, a 13-year-old girl went missing in Seaside, California, and investigators suspected that she had been murdered by her stepfather. However, her body was never recovered. More than 20 years later, a woman appeared and claimed to be the missing girl, but those around her were suspicious of the woman being an imposter. Investigation Discovery’s The Curious Case of … the Girl Who Died Twice, which aired on Monday, January 20, follows the story of Mary Louise Day, her mysterious disappearance and whether or not she really returned decades later.

The docuseries episode began in Fayetteville, North Carolina. A woman narrating the intro explained, “This is one of the last houses she lived in North Carolina.” The woman received a call asking her to come over and added, “Everything after that was a mess.”

The narrator, an older woman standing outside of a trailer, continued, “As I open the door, she’s standing across the room, and she threw a beer bottle at my head. And it broke over my head.” She also described the mystery woman trying to swing at her and screaming at her, describing the woman as being like “The Exorcist.” The narrator said she let the woman in her house with her children, but she “didn’t know her.”

Legal analyst described this story as one about “family and identity. In 1981, a 13-year-old goes missing in Seaside, California.”

The narrator from the intro was revealed to be Mary’s half-sister, . She explained that when she was young, she was told that Mary “ran away,” and she always wondered what happened to her. After a belt buckle and teddy bear were found by police, they began to suspect that Mary was murdered.

“So I looked it at that, we were probably going to be looking for a body,” an officer said.

After 22 years, police finally caught a break in the case — seemingly Mary Day herself.

“A traffic stop changed everything,” Beth explained, and officers described pulling over a woman with the same name and date of birth as the missing Mary Louise Day.

However, doubts quickly emerged that this was truly the missing Mary Day from 1981.

Sherrie explained that she had been searching for Mary “for about 35 years.” After her half-sister went missing, Sherrie “walked around with a hole in my heart wondering what happened to her.”

“My fear is that my birth mother [] and her [third] husband, had murdered my sister,” she added.

Sherrie revealed that her mother’s first husband was a man named . However, while Charlotte was married to Hubert, she had an affair with a man named Charles Day — Mary’s father, as well as the father of Mary’s sister, Kathy — and eventually married Charles. During Charlotte’s marriage to Charles, she had an affair with Sherrie’s father, . Charlotte later had another affair with William, whom she married after leaving Charles.

Sherrie claimed that her mother didn’t want to be a mom and felt like she was “stuck” with her children. She recalled Charlotte attempting suicide.

After Charlotte’s suicide attempt, her three daughters were taken in by the Walts family in New York until she and William got married and were awarded full custody. However, Sherrie said she “hated” her mother and urinated on her when Charlotte came to pick the girls up from their foster home. Charlotte then allegedly turned the car around and returned Sherrie to the Walts family, who later adopted her. She stayed in New York while Sherrie and the rest of her family moved to California.

Sherrie said that one day, she received a letter from her sister Kathy, which had a New York address. Since her family was back in the state, Sherrie’s adoptive parents drove her to see them, and Charlotte informed her that Mary had run away. Sherrie believed her, but when she asked for pictures of Mary, Charlotte allegedly claimed that she “burned them.”

“When I got old enough, I started looking,” Sherrie said of Mary.

Officer , who was investigating Mary’s case, explained that she still had not been officially reported missing in 2002. “Her social security had never been used. You could not find evidence of her having or applying for any identification,” he added.

The officer reached out to Kathy, who said there “was an incident one night,” and she never saw Mary again.

According to Kathy, she and her sister were home while their parents went out to eat. They were told to watch the dog, who was sick at the time. When William and Charlotte came home, William allegedly accused the kids of “poisoning the dog.”

Mary denied the accusation and was told to “go to her room and shut the door” by Charlotte. Kathy claimed that she saw William beating Mary through the door. Mary was not there the next morning, and when Kathy asked her mom what happened to her sister, Charlotte claimed that she “ran away. We’re not to talk about her anymore.”

Soon after that, the family moved to base housing at Fort Ord in California before moving back to New York.

Kathy was brought back to Seaside for the investigation, and she showed Officer Bertaina a spot in her former backyard where William allegedly told her not to play in after Mary went missing.

“William Houle likely murdered Mary Louise Day, and buried her in the backyard, possibly with the help of Charlotte,” retired Seaside detective said.

A forensic team and cadaver dogs were also brought to the backyard, and all four dogs alerted to the same spot. A dig team was ordered, and a little girl’s shoe was found. They also found a belt buckle, but no body.

“At this point, we needed to talk with Charlotte and William,” Joe said.

A search warrant was issued for Charlotte and William’s home in Kansas, where they were living at the time of the investigation, and Charlotte was interviewed. “It was very revealing, you could tell she had some deep concerns about this investigation and that she was being looked at,” Steve said, adding that “it was really apparent she was worried.”

Charlotte allegedly claimed that she and William reported her missing to the Salinas Police Department in California. However, she later claimed that she “gave a bus ticket” to Mary to Salinas instead.

William was also interviewed and pressed on the incident with the dog. He first claimed that he didn’t remember a dog, but later said, “Yeah, I do remember that dog. She killed my dog.” William also said he “may have” hit Mary in the throat, and recalled Charlotte telling him, “You had a demon in you last night.”

William denied killing Mary, but added, “The demon could have killed Mary.”

“That’s as close to a confession as you’re going to get out of someone,” Beth said. However, without a body, the district attorney (DA) wanted more evidence.

During her search for Mary, Sherrie found another sister named , the daughter of Charlotte and Hubert. She found Jeanne through Charlotte’s sister, Louise. “Every time I talk to Louise, I always felt like she knew more about my mother’s story than what she would tell me,” Sherrie said.

Steve recalled getting a phone call from one of his captains, who stated that a woman in Phoenix, Arizona, was pulled over in a truck with stolen license plates. The driver had ID with the name Mary Louise Day and the same date of birth as the missing teen.

After Sherrie heard that her sister had been arrested, she said she received a call from the woman claiming to be Mary, who said, “Is this my sweet little curly red-headed sister?”

In an interrogation, Mary was asked where she lived, and she said she resided in Modesto, California, and other places in Arizona. Mary did not know basic details about her childhood and her family. She also didn’t recall the dog or being assaulted by William.

“Under most circumstances, I think most people would remember that,” , who interviewed her, said.

Police requested a saliva sample from both Mary and Charlotte before her release. She then went to live with Sherrie, who described Mary as “scary” and hoped she wasn’t really her sister.

Sherrie recalled Mary not knowing her own birthday or her father’s name. She also said there were a lot of “fights” while they lived together.

“I really did think she was crazy. Mentally ill,” Sherrie said of the woman claiming to be her sister.

While taking Jeanne to “one of the last houses she lived in” while living with Mary in North Carolina, Sherrie described the woman as having multiple personalities that would change daily. Mary allegedly had a “bad alcohol habit” and didn’t like the rules Sherrie had set. She ultimately moved Mary into a trailer. However, when Mary once asked Sherrie to come over, she threw a beer bottle at Sherrie’s head.

Mary then went back to Arizona, and Sherrie continued to believe that the woman was not her sister. However, the DNA test proved that Charlotte was indeed the mother of the woman in question, known in the investigation as “Phoenix Mary.”

Five years later, when Steve was appointed Chief of Police of Seaside, he asked another detective to look into Mary’s case again. The detective learned that Phoenix Mary actually had a different date of birth of two years earlier.

Sherrie theorized that Charlotte had more children that she didn’t know about. Phoenix Mary might have been one of Sherrie’s sisters, but not the one she was looking for.

In 2017, new Seaside Chief of Police received a call from a “younger sister of Mary Day” informing her that Phoenix Mary was in Warsaw, Missouri, and on hospice care after a battle with cancer.

Before her death, Phoenix Mary said she recalled running away from home, though she was “not sure exactly when or how.” She said she wanted people to know she was not missing. She was taken in by a woman named B.J. Ward. Mary died nine days later.

A former boyfriend of B.J. found a photo of young Mary, whom Judy identified right away as Phoenix Mary.

“There was nothing we could do but close the case again,” Judy said.

Sherrie went to Kansas and visited her mom, who lived in a nursing home. She hoped to finally get answers about Mary. A title card stated, “Sherrie’s mother, Charlotte, declined to be interviewed for this documentary.”

After leaving the nursing home, Sherrie said, “She denied everything. Everything, and all of it.”

There are still conflicting opinions about Mary. While Judy believed that Phoenix Mary was the missing teen Mary, Steve said she may have been a relative of Mary. Sherrie believed that Mary was killed.

Beth explained that Kathy was eventually able to piece together an old memory of driving with William to their home in New York. William allegedly stopped in Utah, took an oriental rug from their trunk and left it in the desert. Kathy claimed that William told her to look ahead the whole time, and he allegedly returned to the car covered in dirt.

The episode ended with a card reading, “William Houle has denied any wrongdoing in the disappearance of Mary Day. He did not respond to producers for comment.”