‘The Staircase’ star Cullen Moss spoke EXCLUSIVELY with HL about Jim Hardin’s ‘humanizing’ moment, working with Parker Posey, and Michael Peterson’s reaction to the series.

The true cause of Kathleen Peterson’s death is the biggest mystery of ‘The Staircase’. Was she murdered? Or was it a tragic accident? These are the three most plausible theories as to how Kathleen ended up dead at the bottom of a staircase in her mansion.