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While filming a TV show, actors naturally develop not only friendships but also a mutual understanding of their characters. However, in the case of John Lithgow’s role on Dexter, the actor himself was far more in the know about what would happen next than any of his castmates, including series star Michael C. Hall. Here’s why.

John Lithgow gave an Emmy-winning performance on ‘Dexter’

Actors John Lithgow and Michael C. Hall pose at the afterparty for the premiere screening of Dexter Season 8
Dexter stars John Lithgow and Michael C. Hall | Kevin Winter/Getty Images

Dexter debuted on Showtime in 2006 and became one of the network’s most popular and award-winning original series. Michael C. Hall plays a forensic technician who maintains a secret life as a serial killer who hunts down murderers. That moral ambiguity is heightened over the course of the series, especially as Season 4 started.

Midway through the show’s eight-season run, Lithgow joined the cast as Arthur Mitchell, a family man and church deacon who becomes known as the infamous Trinity Killer. The character quickly became a fan favorite for his tragic backstory and complex relationship with Dexter. Lithgow even won the Primetime Emmy that year for Outstanding Guest Actor in a Drama Series 

Lithgow was the only cast member who knew the Trinity Killer’s story

Lithgow recently discussed his experience working on Dexter in a video for GQ. As it turns out, the actor knew much more of Arthur’s story than he was supposed to know while filming the show. As he explained, this was simply an unintended byproduct of the casting process:

“I got a terrific pitch from [showrunner] Clyde Phillips. He and John Goldwin, the producer, sat with me at CAA and banished my agents and said, ‘No, nobody else can hear this, and you can’t tell anybody about this. But we are going to tell you about the Trinity Killer.’ And they told me the entire detailed unfolding story. … They had given me way, way much more information than they had intended. But they were trying to persuade me to take the part. … The curious thing was I met all these wonderful actors in Dexter, this whole company of actors. They had kept all this information from them. So I was the only person who knew.”

Ironically, even after he learned the whole story, Lithgow initially turned Dexter down. Thankfully for fans, the actor’s agent and lawyer convinced him to play the Trinity Killer. And just like that, Dexter landed one of its most thrilling characters.

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Lithgow even reprised the role of Arthur Mitchell in the 2021 revival of Dexter: New Blood for a single episode. Now the actor is back with another high-profile TV role, this time as an FBI agent on the trail of a fugitive and former CIA operative (Jeff Bridges) in The Old Man.

The FX series premiered in June 2022 to strong ratings and even stronger reviews. The Old Man has even been renewed for a second season already. While there’s no telling where the show’s story might go, it’s plain to see how Dexter set the standard for Lithgow’s TV work so far.