In May 2001, 17-year-old Alissa Turney vanished on the last day of her junior year of high school — and hasn’t been seen since.

For years, the Arizona teen was believed to be a runaway, thanks to a note claiming she had taken off for California. But holes began to emerge in that theory: Alissa left behind all her belongings, including her cell phone and car, and the nearly $1,800 she had saved in the bank remained untouched.

Over time, family and friends started to believe something more sinister had occurred to Alissa — and alleged that someone close to her was to blame. In 2008, the investigation into her disappearance was reopened, and her stepfather, Michael Turney, emerged as the prime suspect.

Still, it would take 12 more years — and a campaign led by Alissa’s younger sister, Sarah Turney — to bring charges against Michael. In 2020, Michael was arrested in connection with Alissa’s disappearance, but walked free after a judge acquitted him of all charges due to insufficient evidence in 2023.

Now, a new documentary attempts to shed light on Alissa’s case, which remains unsolved. Family Secrets: The Disappearance of Alissa Turney premieres on Sunday, Oct. 13 at 8 p.m. ET/PT on Oxygen True Crime. Peacock will stream an extended version of the documentary beginning on Tuesday, Oct. 22.

So what happened to Alissa Turney? Here’s everything to know about the disappearance case and the different turns it has taken over the past two-plus decades.