Credit: Isabella Vosmikova/USA Network

In the fourth episode of Dirty John: The Betty Broderick Story, devious attorney Dan Broderick (Christian Slater) drops a bomb on his suspicious wife, Betty (Amanda Peet): He always wanted to sleep with his receptionist, Linda (Rachel Keller), and now he's admitting it straight up.

"Tell me I was right the whole time," Betty demands mid-fight. Dan hits her with the nail in the coffin for their marriage: "You were right the whole time."

Throughout the first half of this season, which has seen intentional car crashes and way too much Boston cream pie on a bedsheet, Betty has been on a spiral since Dan left the house. It was a last grasp at saving his and Betty's relationship, which began in 1969 San Diego with a growing family full of dreams of promotions and perfection.

As things go south, Slater tells EW that his performance was partly inspired by the 1944 film Gaslight, starring Ingrid Bergman and Charles Boyer.

"His performance in that is insidious, sneaky, and sadistic," Slater says of Boyer. "You're driving somebody crazy and also enjoying the power that he believed he had. He thought he was untouchable after he built up so much success."

Dan is never more heinous than in episode 4, "More to It Than Fun," which focuses on his relationship with Linda over 14 months as he ultimately leaves Betty for her. "To a large degree, this is a very classic story," Slater says. "A man gets supported by the woman while he's learning how to be doctor or lawyer, and then he begins to build a wedge between the two."

Below, Slater tells EW about his character's motivations, how Dan parallels his 2017 performance in Glengarry Glen Ross, his camaraderie with the film crew, and more.

ENTERTAINMENT WEEKLY: It seems like Dan Broderick has a lot in common with some of your past roles. They have a coldness to them, a bit of nastiness to them. How did you sink your teeth into the role of Dan?

CHRISTIAN SLATER: It was challenging. You know, we had to do a lot of various takes. I would have a particular way of saying a line; they would continue to tell me to be meaner. I felt it became hilarious to a certain degree. The crew would say to me, "God, we like you so much, but we hate you when the camera's rolling." I would just have to remind myself it's the character, not me. It was to the point to where I would say after a take, "well, that was pretty great!" And because the crew and I got along very well, they would hiss at me. Make that snaky sound. It had a layer of humor.

Going deeper about your past roles, you played Ricky Roma in a 2017 production of Glengarry Glen Ross in London, and I find that character to be of the same world as someone like Dan. Here's a guy who thrives on greed, manipulation, and power.

You never know how one thing feeds into another, but as you bring that up, I think it's a very interesting observation. By playing that character, there probably were qualities and characteristics that I did end up bringing into Dan. Doing Glengarry Glen Ross was a fantasy of mine. Everyone wants to do a David Mamet production. What's very clear in David Mamet is that there's a particular rhythm to all of those scenes and every line that he wrote. You really just have to get into his rhythm.

Dan also seems to exemplify a certain late-'80s, early-'90s kind of toxic masculinity. Is there something you like to explore in a character like that?

[Series creator] Alexandra Cunningham does play with the levels of egotism and narcissism. Dan is a guy in a power struggle. He wanted to take on the world. Some people think, had he lived, he could have easily gone into politics. Dan was able to manipulate the system and use his knowledge and connections that he had to get into that power position. There's torture and then there's emotional torture. Betty was put through horrible emotional torture. It's one of the cruelest things you could possibly do.

Credit: Isabella Vosmikova/USA Network

Let's talk about the end of the episode: You have a really powerful moment where Dan basically tells Betty he's been in love with Linda the whole time. That the white lie he told months ago had snowballed into cheating. What do you remember of that scene on set?

It was one of those moments that we took very seriously. We tried it in many different ways. We tried it with some compassion, we tried it with as much heart as we could. We just went through the subtle differences until eventually we got what we wanted: cold and calculated. Betty obviously was driving him crazy, but what's also unfortunate about that is that they lived through it during the '80s. I don't think you could get the same kind of help that you can get today. I wish that they had given themselves that opportunity. Whether they would have or not, I don't know, but to have someone mediate or to communicate clearly would have been obviously helpful.

Dirty John: The Betty Broderick Story airs Tuesdays at 10 p.m. ET on USA Network.

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