What turns someone into a serial killer? In the 1970s, the FBI was utterly in the dark. But a wave of seemingly unmotivated killings – by Charles Manson, David Berkowitz, Ted Bundy and John Wayne Gacy – forced them into uncharted territory. A new form of profiling was required, one that didn’t simply believe evil to be genetic, but took into account one’s formative years.

Netflix’s ambitious new drama Mindhunter explores the early days of the serial killer. Based on a book co-written by John E Douglas, the FBI agent who was the inspiration for Clarice Starling’s mentor Jack Crawford in The Silence of the Lambs, it’s also created by David Fincher, director of Seven and Zodiac.

“It seems like our culture is obsessed with serial killers,” Jonathan Groff tells me in the library of a Manhattan hotel. He plays a fictionalised version of Douglas, a young agent crossing the US to conduct harrowing interviews with serial killers about their motivations. It’s a far cry from Groff’s prior work – he has starred in Glee, the acclaimed HBO drama Looking, the hit Broadway musical Hamilton, and voiced iceman Kristoff in Disney’s Frozen.

‘Our culture is obsessed with serial killers’ … Mindhunter. Photograph: Patrick Harbron/Netflix

Mindhunter arrives during a renewed obsession with true crime – the success of Serial, Making a Murderer and The Keepers all providing fertile ground for a show that explores the origins of techniques we now take for granted. “All my friends while I was working on the show were in anticipation,” Groff says. “Friends you wouldn’t expect to be interested in the minutiae of how someone ripped apart a body and fucked their neck.”

Groff laughs but there is a strange truth here: a prestigious, high-end drama like this provides a socially acceptable way to explore evil. It’s tough stuff and Groff admits that the gruesome facts were often difficult to swallow.

“I had a hard time making it through the book,” he says. “I had to keep putting it down. Ultimately, we’re actors, I’m putting on a costume, so we’re playing pretend. But then I would walk into the makeup truck and there’s a scalped woman’s head and you go, ‘Fuck!’ You think, ‘Oh shit, this really happened, this is so intense.’ Then you just kind of shake that off and have a drink or have a laugh with Fincher.”

The phrase “have a laugh with Fincher” isn’t one you hear often. The director, whose films also include The Social Network, The Girl with the Dragon Tattoo and Gone Girl, is known for his meticulous nature (while shooting Fight Club, he took more than 1,500 rolls of film – three times the average in Hollywood). Zodiac star Jake Gyllenhaal once called him a “disciplinarian”.

“There’s no pretension,” Groff says of Fincher. “Yes, he’s meticulous and, yes, occasionally there’s multiple takes but it’s really because he wants it to be good. It was so fucking amazing. I have withdrawal.”



‘You think you’re playing pretend, then you realise “Fuck!” this really happened’ … Mindhunter. Photograph: Merrick Morton/Netflix

It’s a show Netflix clearly has confidence in, giving the green light to a second season before the first has even aired. It’s also set to provide Groff with yet another fervent fanbase. His role in Andrew Haigh’s critically acclaimed (but short-lived) drama Looking, about the lives of gay men in San Francisco, led to a loyal gay following who welcomed rare representation on screen, even if it received criticism for not being gay enough, being too gay, and not being diverse enough.

“The cruelty was confusing,” he says. “And it was a bummer because that happened at the very beginning. The show might have gone on longer if we’d had a more supportive start, but the aggressive negativity was disappointing.”

Groff is something of a rarity: an openly gay actor working in Hollywood, headlining a major drama as a straight character. “If I’ve had roadblocks along the way for being gay, I’m not aware of them,” he says. “I haven’t had anyone say no, we can’t because he’s gay. In fact, it’s been quite the opposite. Sex is such a huge part of Mindhunter and never for a second did I feel self-conscious sharing my own stories in the creative process. It was very fluid and free and open. Being a gay person didn’t affect anything about it, but being able to share my relationship history and my sexual history as Jonathan – that affects everything when you create a character.”

‘Kids don’t get that I’m not blond and a cartoon!’ … Groff as Kristoff in Frozen. Photograph: Disney

The 32-year-old’s most widely seen character remains Kristoff in the $1.2bn smash Frozen, a film he refers to as “like crack for children”. He’s just started work on the sequel. “Kristin, Josh, Idina and I are on a text chain where we make voice memos as the characters to auction off for kids or kids with cancer,” he says. “It’s so fun to be a part of that and get them more excited. Often there are a lot of hilarious awkward moments when parents are like, ‘This is Kristoff from Frozen?’ They’re like, ‘What?’ They don’t understand that I’m the voice of the thing. I’m not blond and a cartoon.”

His most notable fan is none other than Beyoncé, who approached him after she saw Hamilton to compliment his performance and his walk, which she proceeded to impersonate. “This is going to sound so weird and stalkery, but I just feel blessed to have been in her presence and shaken her hand. Nothing that I could have said to her could have articulated the depth of my feelings for her.”

Groff wasn’t part of the Hamilton cast when vice-president Mike Pence attended to the sound of boos and a speech (“classy and heartfelt,” Groff says of their words) but there’s an odd political parallel in Mindhunter. The show revolves around the difficulty inherent in finding empathy with those you find distasteful, and how the intellectualism of the FBI was seen as an affront to smalltown police at the time.

“Trump got elected while we were in the final months of shooting so it wasn’t like we were making this show with that in mind,” says Groff. “But I can’t help but think, when I watch it back, the idea of how divided everybody is. The idea of faking empathy to take a step forward to understanding – it’s a really powerful idea.”