Michael Peterson was living the American dream: With a successful writing career, a beautiful family, and a picturesque home in Durham, North Carolina, he and his wife Kathleen seemed to have it all … then everything changed.

In the early morning hours of December 9, 2001, Michael called 911 to report that his wife was unconscious and lying in a pool of blood after possibly falling down "15, 20, I don't know” stairs in their home. Michael claimed it was a tragic accident and said that his wife had been drinking and taken some Valium. But the police, and armchair detectives around the world, had other ideas—namely, that Michael was to blame.

For nearly 20 years, the mystery surrounding Kathleen Peterson’s death has only grown, especially in the wake of Michael’s trial—where he was found guilty, but later managed to walk free—and the number of sometimes-odd theories that have sprung up to explain what happened (including the idea that she was attacked by an owl).

The case has been featured on a number of true crime series, including Dateline and Forensic Files, and spawned a 2004 docuseries, The Staircase, directed by Oscar-winning filmmaker Jean-Xavier de Lestrade. Now, Investigation Discovery is going back to the scene of the crime for a three-part series, An American Murder Mystery: The Staircase, which will premiere on Sunday, April 8 at 10/9c.

“The death of Kathleen Peterson is one of the most confounding cases in history,” Henry Schleiff, group president of Investigation Discovery, American Heroes Channel, and Destination America, said in a press release. “There are so many pieces to this puzzle—from Michael’s salacious secrets to investigator misconduct to the odd owl theory—so, we are eager to bring our viewers the first complete look at this fascinating crime and subsequent trial.”

Another theory? The “blow poke” theory, which Kathleen’s sister Candace explains in this exclusive clip below.

An American Murder Mystery: The Staircase will premiere on Investigation Discovery on Sunday, April 8 at 10/9c.