New Documentary Explores Mysterious Disappearance of Ariz. Teen Alissa Turney — and Sister's Quest for the Truth (Exclusive)

Sarah Turney was 12 years old when her half-sister, Alissa Turney, 17, suddenly vanished in May 2001. She never was able to say goodbye as Alissa disappeared on the last day of her junior year at Paradise Valley High School in Phoenix, Ariz.

When Sarah got home later that day, she found her sister’s bedroom wrecked, with a note on her dresser explaining that she’d run away to California. To Sarah, this seemed plausible. Yet Alissa left her cell phone and makeup behind, details that would later strike investigators as peculiar. Their father, Michael Turney, a former sheriff's deputy and electrician, called in a missing persons report that evening.

Police in Phoenix initially thought Alissa might have run away from home. But as years passed with no sign of her, Sarah Turney, now 35, came to believe that Alissa was not a runaway but a victim of homicide.

In a new documentary Family Secrets: The Disappearance of Alissa Turney, which premieres Sunday, Oct. 13 at 8 p.m. ET/PT on Oxygen True Crime, Sarah, an executive producer on the film, alongside New York-based media company Story Syndicate, delves even deeper into the facts of the case and uncovers some chilling discoveries along the way. Peacock will stream an extended version of the documentary beginning Tuesday, Oct. 22.

"Looking back," she says, crying to the camera — in the trailer debuted exclusively by PEOPLE — "I was just trying to pretend everything was fine."

Moments later, she adds: "I really wanted to get to the truth of what happened in my family. That's one of the biggest questions in this case is why didn't anyone do anything? I realized that it was all on me."

The more Sarah searched for answers, the more convinced she was that the man who gave her life was the same person who took her sister's. "For me, it was kind of like a switch," Sarah explained to PEOPLE in December 2020.

Despite Sarah’s suspicions, Michael Turney has steadfastly asserted his innocence, including during a 20/20 interview with John Quiñones in 2009. He was acquitted of murder charges just last year.  

Sarah was 4 years old when Alissa's mother, Barbara Strahm, died of lung cancer. The girls grew up in a blended family, as Alissa's mother remarried a year before she passed, and her stepfather Michael adopted her.

Each of Turney’s five other children have said they believe he is responsible for the disappearance of their sister. Most vocal among them has been Sarah. As an adult, she launched a podcast, a Facebook group, an Instagram account and finally, TikTok, airing details about her sister’s relationship with their father, including conversations they’d had and interactions with law enforcement she believes are incriminating.

Sarah's videos, which have garnered over a million followers and some have been viewed more than 20 million times, were part of a campaign undertaken at the behest of detectives, who urged her to get more attention on Alissa’s cold case. Turney has also founded a true crime media company that hosts her podcast, “Voices for Justice,” and “Media Pressure,” led by Julie Murray, which empowers victims of violence and their loved ones to speak out.

Ultimately, Alissa's remains were never found. Sarah's online petition got nearly 300,000 supporters urging a murder trial against her father Michael. Eventually, the police opened the case as a murder investigation in 2006, after Alissa's boyfriend told them that Michael had checked her out of school the day she went missing. He was charged with second-degree murder in 2020, but a judge acquitted him in July 2023 because of insufficient evidence. Sarah continues to post to TikTok what she claims is evidence of her father's guilt.

In the trailer, Sarah confronts her father Michael in an emotional conversation.

"I'm trying to meet you in the middle here, Dad," Sarah says to him.

"You've destroyed your own family," Michael says to his daughter.

"You're trying to gaslight me and I'm not taking it," she responds angrily.

“As filmmakers, we wanted to explore the shifting nature of truth and how someone who had been groomed to believe one version of reality could relearn her own memories,” said the documentary's directors Ricki Stern and Jesse Sweet, also an executive producer. “We crafted the film to embody Sarah’s journey of excavating the truth about herself, her family and what happened to her sister. We are grateful to Sarah for welcoming us into her life and opening up her family archive in support of this vision."

Family Secrets: The Disappearance of Alissa Turney, which is produced by Dan Cogan, Liz Garbus, Jon Bardin, Kate Barry, Mala Chapple, Ricki Stern, gives unprecedented access to the continuation of this tragic story, including a recently unearthed trove of never-before-seen home videos, as Sarah re-examines her and Alissa’s childhood. In this documentary, Sarah pushes through the years of torture, anguish and manipulation in her attempt to reconstruct the truth — to figure out their past and break free of her father's influence.

Peacock’s extended version of the documentary, out a week after Oxygen True Crime, will include expanded and new sections of the film. Notable footage includes Alissa’s friends providing intimate details of their friendship with her, an investigation of Sarah and Alissa’s father Michael's disturbing relationship with Alissa and other family members and friends. It will also provide a deeper look at Sarah’s advocacy on social media and through her podcasts.

"It's not a dirty family secret," Sarah continues during the trailer. Looking straight to camera, she says: "It's about what's right and what's wrong."

Family Secrets: The Disappearance of Alissa Turney premieres Sunday, Oct. 13 at 8 p.m. ET/PT on Oxygen True Crime. Peacock will stream an extended version Tuesday, Oct. 22.