'The Staircase': A Guide to the Family, Theories and HBO Max Series (Exclusive)

The Staircase

The true-crime series re-examines the life of Michael Peterson and the unexpected death of his wife, Kathleen.

The Staircase, the captivating HBO Max true-crime series, explores the complicated lives of Michael Peterson, who is suspected of killing his wife, Kathleen, after she is found dead at the bottom of the stairs, and members of his large family, who are trying to cope with the unexpected death of their matriarch and all the revelations that emerged in the investigation that followed. 

Inspired by the real-life story that was first captured in the Netflix docuseries of the same name and later lampooned in season 1 of NBC’s Trial & Error, the limited scripted series adapted by showrunners Maggie Cohn and creator Antonio Campos features an all-star cast, including Colin Firth as Michael and Toni Collette as Kathleen as well as Dane DeHaan, Odessa Young, Olivia DeJonge, Patrick Schwarzenegger and Sophie Turner as their various kids. 

Additionally, Juliette Binoche, Michael Stuhlbarg, Parker Posey, Rosemarie DeWitt, Tim Guinee and Vincent Vermignon appear as extended family members and other people involved in the investigation. 


While Michael’s story may be familiar to some, especially given the attention that surrounded the many iterations of the docuseries and the scripted parody that followed, ET has put together a guide to the sprawling Peterson family, the various theories surrounding Kathleen’s death as well as the ins and outs of the HBO Max series. 

“While it feels like this story has kind of been told before, the reality is there's so much of the story that hasn’t been explored,” Campos said, with Firth adding that this version “messes with your expectations.” 

The Peterson Family

Michael’s immediate family is quite large – and quite layered – especially considering it’s a blended family made up of kids from previous marriages and the adoption of two daughters. All of them are featured here, as The Staircase “lets you experience what it’s like for a family to be going through something like this and allow a documentary to be made while that’s happening, which is also kind of an incredibly powerful thing to go through and agree to go through,” says DeHaan, who plays Clayton.   

  • Caitlin Atwater (DeJonge) is Kathleen’s biological daughter from her first marriage to Fred Atwater (Jason Davis). While she was happy to call Michael her stepdad, she came to suspect him of killing her mother and later filed a wrongful death suit against him. 
  • Clayton (DeHaan) and Todd (Schwarzenegger) Peterson are both of Michael’s biological sons from his first marriage to Patricia Sue Peterson (Trini Alvarado). They both staunchly supported their father and believe he’s innocent, with Todd theorizing that Kathleen’s death was alcohol-related. 
  • Margaret (Turner) and Martha (Young) Ratliff are Michael’s adopted daughters. Their biological mother is Elizabeth Ratliff, the widow of Michael’s best friend. Elizabeth also died at the bottom of a staircase while they all lived in Germany, a revelation that casts doubt on Michael’s innocence. Despite the similarities in Elizabeth and Kathleen’s deaths, both girls supported their adopted father throughout the investigation and trial. 

In addition to Kathleen and Michael’s children, other key family members seen throughout the series are Kathleen’s sister, Candace Hunt Zamperini (DeWitt), who is convinced of Michael’s guilt; Michael’s brother, Bill (Guinee), who helps care for the family and with the defense in the wake of Kathleen’s death; and Sophie Brunet (Binoche), a woman who supports Michael later in life. 

The Many Theories 

When it comes to what actually happened to Kathleen, no one knows for certain, despite the fact that Michael was ultimately found guilty of her murder and later entered an Alford plea, which acknowledges there’s sufficient evidence to convict him but he maintains his innocence, to voluntary manslaughter.


In fact, there are several theories about Kathleen’s death, including everything from her slipping down the stairs to an owl attack that left her dead. These are the most prominent ones: 

  • An intoxicated Kathleen fell backward down the stairs, where she succumbed to her injuries before help could arrive. This theory was one that Todd often suggested during the investigation. 
  • Michael attacked Kathleen with a fire poker before leaving her dead at the bottom of the stairs. This is one Candace supported after it was discovered the family gift she gave her sister was missing. 
  • Michael pushed Kathleen down the stairs just like he did to Elizabeth, who died under similar, mysterious circumstances. The prosecution was convinced this is what inspired Michael to do what he did to Kathleen. 
  • Because of the marks on Kathleen’s skull and the fact that there were feathers in her hand and a tree sliver was found in her hair, neighbor Larry Pollard (Joel McKinnon Miller) believed a barred owl attacked Kathleen before she eventually fell down the stairs.

Many of the theories are recreated in the series, with Collette “there for all the deaths,” she says, before revealing that she and a stunt woman recreated variations of Kathleen’s falls down the stairs. “It was quite choreographed… And often it was only one take. I had only one take to do it. There were three deaths, and two of the three were one take. And the last one, the owl one, was two takes.” 

Because of all the theories, the cast was “flip flopping” over what happened to Kathleen. “It’s very difficult. No one will ever know,” Collette says, with Schwarzenegger adding that it was “frustrating” at times “because you want to be able to pinpoint what happened.” 

“And I think that’s what makes this story so fascinating,” he continues. “Because you are almost 100 percent sure it was Michael Peterson that killed her. Then there’s ways that couldn’t add up and you believe she could’ve fallen down the stairs.”

Schwarzenegger adds, “There’s so many things that could be possible.”


While they researched all of the theories, Cohn says they stuck to “the ones that felt viable.”  

“In terms of deciding which theories to visually represent, it was important to represent one in which it was a horrible accident that happened at home that makes your heart stop because it could happen to anyone,” Campos says. “And then there’s a scenario in which somebody is fully responsible for her passing away. And then the next scenario is that something freaky, one-off thing just happened, which then precipitated her death.”

He adds that when it comes to the latter, “the owl represents chaos. Like, these are things that just happen.”

The HBO Max Series

While most true-crime series examine (and attempt to solve) the crime at hand, The Staircase is really an investigation into the genre itself. “Instead of searching for a single truth, this was an opportunity to explore a tragedy from multiple perspectives and offer narratives that each one of these things could have happened and were viable,” Cohn said, with Collette adding that it’s “about a family and relationships” and how that all played into what followed in the case. 

Not only that, but the series shows all the components -- from the making of the documentary to the theories that later emerged -- that were all part of this complicated saga. “There’s so much to this story,” Campos said, explaining that while the docuseries zoomed in on the family drama at the center of the case, the scripted series pulls back the lens to capture “all the personal dynamics at play.” 

And that’s “not just within the Peterson household,” he continued, noting that those dynamics also include “Kathleen’s sisters, the DA office and these side characters that were witnesses and played a major role in the story, like [medical examiner] Deborah Radisch.” 


“We’re just interested in the humanity of it all and exploring them,” the showrunner added, explaining that it’s less about the physical evidence and more about “the people that were gathering the evidence and reporting the evidence and processing the evidence – and exploring them and trying to understand a little bit more about who they were and why they interpret the evidence the way that they did.”

While there is a mysterious crime at the center of the series and subsequent trial that resulted in a contentious conviction, The Staircase is really about how people construct narratives to fit their personal perceptions, especially when it comes to who Michael is and what they think about him. “We’re trying to look at it all holistically and understand why people are doing that,” Campos concluded.

Additional Streaming

As Campos explained, “We were going off of a lot of different sources.” 

“The documentary is just one source. It’s kind of where the journey started for us, but wasn't the only thing we’re referring to,” he said, referring to Diane Fanning’s nonfiction novel about the case as well as many articles, original interviews and “all the stuff from the trial and investigation.”


So, if the series is not enough to satisfy interest in all things Michael Peterson, there are several other projects audiences can stream, including the previously mentioned Netflix docuseries, Trial & Error and the Criminal podcast:

  • The Staircase (Netflix): Jean-Xavier de Lestrade’s docuseries was originally released in 2004 as a French miniseries. Following the success of the series, Lestrade reunited with Michael and his family in 2012 for a sequel. Three new episodes were later made for the 13-part version that’s now streaming on Netflix. 
  • Trial & Error (NBC): Season 1 of the legal mockumentary stars John Lithgow as eccentric poetry professor Larry Henderson who is accused of murdering his wife. Despite his lawyer’s attempt to prove his innocence, including the discovery of a piece of evidence suggesting a bird was responsible, Larry has an uncanny way of implicating himself in the case. 
  • “Animal Instincts,” Criminal (Vox Media): Not included in the docuseries is the owl theory made popular by the Criminal podcast, which recounted Pollard’s convincing argument that a bird of prey was actually responsible for Kathleen’s death. 
  • Written in Blood: A True Story of Murder and a Deadly 16-Year-Old Secret That Tore a Family Apart (Audible): Prolific American crime author Diane Fanning wrote the 2005 nonfiction novel about Michael’s case, digging deep into his history as a Vietnam vet to his passion for crime novels before the death of his wife, Kathleen, turned his life upside down and secrets from his past come back to haunt him.

The HBO Max original series, The Staircase, debuts Thursday, May 5 with three episodes, followed by one new episode weekly until June 9.