49 years after the shocking (but forgotten) true story, Bill Skarsgård plays a scorned kidnapper in Dead Man's Wire, a surprisingly funny crime thriller with a near-perfect Rotten Tomatoes score

"There's so much footage of the real event. Like, a crazy amount of footage," Bill Skarsgård tells us of his new film, Dead Man's Wire, which is based on the unbelievable true story of Tony Kiritsis. 49 years ago, Kiritsis walked into a mortgage company building, took the owner's son, Richard "Dick" Hall, as his hostage, and held him captive with a shotgun wired to his neck for 63 hours. Kiritsis asked for nothing more than an apology – and $5 million – after believing the Halls had swindled him.

"Even in the script, as you're reading it, Austin [Kolodney], the writer, had put links in to the actual 911 phone calls, and the footage of them walking on the streets with the shotgun wired to his neck," Skarsgård adds.

This profoundly odd true story forms the basis of My Own Private Idaho director Gus Van Sant's latest film, a taut, tense, and surprisingly funny thriller starring It and Nosferatu's Bill Skarsgård as the aggrieved Kiritsis, and Stranger Things' Dacre Montgomery as his captive Hall.

Stranger than fiction

Just like in real life, the film begins with Skarsgård's Kiritsis walking into the office of Meridian Mortgage Company and kidnapping Hall, using the so-called dead man's wire that gives the film its title. This wire connects Hall to the shotgun's trigger, and the other end goes around Kiritsis's own neck. One wrong move, and Hall will meet a grisly end.

"It was hard to separate the actual event and the film that we were trying to do," Skarsgård explains. "I researched the guy a lot – there's so much footage – and how he looked, and how he spoke, and his mannerisms, and all of it. And then also knowing that we're going to do some of these scenes that are verbatim of what he said on the day…"

But while the film hews extremely close to the true story, Skarsgård doesn't bear much of a physical resemblance to the real Kiritsis at all, something he initially found hard to reconcile. "My way into the character was so tied to the real guy that it just ended up becoming an obstacle for me, because I just felt that physically, I'm so different than the real guy," he says. "And I've played quite a few characters that have been based on real people, but then I've been cast because of some sort of physical likeness to the real guy. It was like, 'Oh, this guy was also tall and my age,' but this was very different. There was just something that I had to get over: I am not physically right for this role or portraying this man."

Van Sant was able to help Skarsgård deal with the discrepancy. "Gus kept just encouraging me that I will have to be portraying my Tony," Skarsgård says. "And some actors I think are quite different than that. You could do this and then separate yourself completely from the real guy, and just be like, 'Oh, who cares?' People don't know who Tony Kiritsis is today, really. He's not a household name. So, you could just separate yourself from him and do whatever the fuck you want to do with the role, or play the character much more closer to yourself, like, 'Okay, this is how I'm going to do it.' But I'm not like that. So, the research component was huge, to the point of getting in the way of me actually doing it."

Tied together

The bulk of the 63 hours Hall and Kiritsis spent together took place in Kiritsis's own apartment. Likewise, the film is mostly set in this dark, cramped space, with Montgomery and Skarsgård shouldering the majority of the screen time. "He was my partner in this. From the beginning to the end, it's just the two of us, really," Skarsgård says of working so closely with Montgomery.

Kiritsis forces Montgomery into a chair with the shotgun on a table in front of him, aimed squarely at his head. Montgomery is a quiet, measured man who weathers his ordeal with weary fear, enduring Kiritsis's ramblings and ravings as, outside, the police plot to save him.

The film was very much a collaborative effort, and Skarsgård was keen to ensure the situation, while fraught on screen, was safe behind the scenes. "It is just the two of us in so many of the scenes, quite literally wired to each other. So, we did have three or four days with just me, Dacre, and Gus, talking through the whole script, talking through our interpretations of our characters and the dynamics," he explains.

"And then we would rehearse a little, and it was a useful time for us to vent and get to know each other," he continues. "Right off the bat, Dacre and I just really got along, which is good and which was really helpful, because it was just really important that we both – or for me, at least, I think he has probably worked a bit different in the past, I know he's expressed it – but for me, it was like, 'Okay, it's really important that we're very safe with each other, and that we trust each other completely,' so we could rely on each other as scene partners, and I think we really did."

Naturally, the dead man's wire had an effect on the dynamic Skarsgård and Montgomery established, too. "Dacre and I became really good friends in the process of it. And I don't think either one of us have ever played two characters that are literally fused together like this. So, it was fun and organic," Skarsgård says. "He would feed to me and I would feed to him. Being fused together, whenever he had an instinct of, like, 'Okay, I want to go right,' and I'll go, 'No, go left!' So, it becomes this ping pong game of whatever he's doing, I'm counter-reacting to it physically."

Unexpected laughs

Despite the seriousness of the film's subject matter, it can be surprisingly hilarious at times. "There was something about the real Tony that I did find funny," Skarsgård says. "Part of the thing that I found so fascinating about the character, he could be menacing and funny and weird and endearing and sad, all in the same five seconds. I'm talking about the real guy. That type of complexity. I don't think he has gotten any sleep at all in the past three days, and so there's this whole manic episode unfolding, and he's really pivoting from emotions, where he could be fueled with black outrage, and then he can be in tears the next second, and then he could make a joke the third."

Much of the humor comes from the inherent absurdity of the situation itself – at one point, Kiritsis parades the captive Montgomery down the street to commandeer a police car after the key breaks off in his own ignition, to the consternation of onlookers and the police themselves, and at another, an officer has to tell him how to operate the police car's PA. There's also Kiritsis's frenzied mannerisms and deranged behavior, which often jar with the reality of the kidnapping: in the apartment, he offers Montgomery, forced to sleep in the bathtub, a donut, and he often apologizes for his behavior, even as it continues.

Even Van Sant was caught off guard. "Gus is a very explorative filmmaker, where he lets the film find itself, and he has a lot of trust in his actors, and he doesn't try to force anything. He gently shapes it and guides it into what the movie becomes, but he trusts the movie in a profound way," explains Skarsgård.

"But I think that the first day of the shoot, we were doing the reception of the mortgage company, and I just started improvising," he adds. "Tony… [there was] something just funny and bizarre about the real guy, but also what I was doing with the character. I remember Gus coming up to me, and he goes, 'Hmm, this is funny.' It surprised him that the movie might be funnier than he initially thought. And I was like, 'Yeah, I think it might be. I think it is.' I don't think Tony's being consciously funny. There's something funny about him, which is a different thing."

In fact, Van Sant didn't realize how funny the film actually turned out until very late in the process. "The first screening he did with friends and family, the whole audience was just laughing so hard, and he was genuinely surprised that the movie had turned out that funny, because he was just so close to it at that point," says Skarsgård with a laugh.

Despite this, though, the film still carries a real sense of pathos. "In a way, they're just two lost sons that never had a good male role model, either one of them," says Skarsgård of Hall and Kiritsis, and a scene in which they call Hall's unsympathetic father, played by Al Pacino.

"And I think that what the two of them are discovering, or at least what Tony is discovering, is that the illusion of coming from money, or having money, doesn't mean that you have everything. There is a genuine sadness in Dick as well, and that they can meet there, almost, briefly, for a moment, before the shotgun's wired onto the neck again and what has to be done has to be done."

Dead Man's Wire arrives in UK cinemas this March 20. In the meantime, check out our guide to all the most exciting upcoming movies of the year, along with the biggest movie release dates.