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As Big Sky Season 2 gets underway, viewers all want to know how much of the TV show is based on a true story? The answer is a bit complicated. It turns out that the inspiration for Ronald Pergman (Brian Geraghty) came from real-life serial killer Ed Gein. However, the most intriguing part is that both of their mothers show a massive number of similarities.

Big Sky Helen and Ronald Pergman talking to each other
‘Big Sky’: Valerie Mahaffey and Brian Geraghty | Darko Sikman/Getty Images

Is ‘Big Sky’ based on a true story?

The ABC series, Big Sky, is based on C.J. Box’s fiction suspense thriller, The HighwayBig Sky Season 1 closely follows the novel, including the death of Cody Hoyt (Ryan Phillippe) early in the drama. The book is the second of six novels in the Cody Hoyt/Cassie Dewell book series written by Box. It begins with the same two girls that start the show in season 1 traveling down a remote highway in Montana.

‘Big Sky’ killer Ronald is based on real-life serial killer Ed Gein

According to IMDb, Ronald Pergman’s character in Big Sky is based on the real-life serial killer, Ed Gein. He committed crimes around his hometown in Plainfield, Wisconsin, in the early 1950s. Gein confessed to killing two women — tavern owner Mary Hogan in 1954 and hardware store owner Bernice Worden in 1957. The convicted serial killer also inspired Norman Bates from Psycho, Leatherface from The Texas Chainsaw Massacre, and Buffalo Bill from Silence of the Lambs.

In Big Sky Season 1, viewers watched as Ronald visited Merrilee Legarski’s (Brooke Smith) local shop. Many times fans of the series thought he might abduct or hurt Merrilee, but he never did. Instead, Ronald kidnapped two young girls who made fun of him on the highway, but generally, he abducted sex workers. 

Serial killer Ronald Pergman and real-life killer Ed Gein had very similar mothers

The mothers of both Pergman and Gein share the most similarities. In Big Sky Season 1, viewers found out that Ronald lived only with his mother, Helen Pergman (Valerie Mahaffey), and he had a strange infatuation with her. 

Both Helen and Gein’s mother, Augusta, was highly religious. According to Men’s News Daily, Augusta preached to her two boys that drinking was evil and all women were promiscuous. After Gein’s father died and his mother moved out, Gein shared that same attachment with his mother portrayed between Ronald and Helen in Big Sky.


‘Big Sky’ Season 1 Recap — The Refresher Viewers Need Before Season 2

In Big Sky, Helen sounds very similar to Augusta in the morality that she preached to Pergman. Both women kept tidy homes and strived for perfection in their boys. However, in many reports about Gein, reviewers of the case noted that his madness stemmed from the way his mother treated him. After watching Helen berate Ronald throughout Big Sky Season 1, it’s evident that she is based on Augusta. 

“Helen, she just took this weak boy and kept stressing her idea of how to be in the world, and just warped the heck out of him,” Mahaffey (who portrayed Helen) told TV Line.

The more viewers read about Ed Gein and his mother, Augusta, the more they will find similarities between the two. Big Sky’s Ronald and Helen Pergman are both based on the real-life killer and his mother.

Big Sky Season 2 airs Thursdays at 10 p.m. EST on ABC.