Sebastian Stan studied 'every serial killer in last 3 decades' for Fresh

And in an exclusive interview with RadioTimes.com, Stan revealed some of the extensive research he carried out to get a handle on the character.

"I have a great acting coach that I work with, Larry Moss, and then I just started reading all these books on narcissism and bipolar disorder and kind of multiple personality disorder," he explained.

"But it was really the extreme narcissism aspect of it that I felt was helpful, and then I stumbled upon some other research in doing so. A lot of documentaries, you know, on Ted Bundy and Jeffrey Dahmer and kind of every single serial killer in the last three decades, I think I looked up."

Stan added that he was also introduced to a doctor by the name of Dorothy Lewis who was "very helpful" in giving him a more detailed look into the minds of these types of characters.

"She had interviewed a lot of these people, and I sent her the script," he explained. "And with her, I was able to check everything – because we want to be able to really ground these characters and him specifically – and then she and I were able to kind of create a backstory for what potentially Steve's childhood was like.

"You know, in order to kind of point the dots to 'OK, well, how did he manage to get this successful? Why and ultimately what was he looking for?' Just all those things. And it was really working with her that was very illuminating in a way."

Asked if playing such a dark character – and looking into so many grisly real-life cases – took its toll on him personally, Stan responded: "I think there was a degree that was a bit exhausting about it.

"I remember we were shooting in Canada in January/February, really cold weather. I had to do a quarantine when I got to Canada, so I was locked up for two weeks in the apartment that I was in, and just watching all this stuff.

"But incredibly, it was very fortunate, because it also focused me in a certain regard. But then, yeah, it just didn't stop... we were working five days a week. And then we were getting together on the weekends. reworking the script and the scenes, and so it was kind of a 24/7 thing for a while.

"But again, I was in such great company, because we had a really great director [first-time feature director Mimi Cave] and our producers were super supportive, very helpful and flexible to ideas, and really just the trust that Daisy and I were able to have together kept everything just moving forward."

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