A thriller about accounting? Oddly enough, it all adds up when Ben Affleck’s autistic bean counter starts uncooking the books for criminals in The Accountant.

Ben Affleck was born to play Christian Wolff, an emotionally remote but laser- focused number cruncher who also happens to be a killing machine, thanks to early training in martial arts and weaponry. He also happens to carry a bigger gun than Jason Bourne.

“It’s a smarter script than what you’d think. If you think of something in the genre of The Bourne Identity or other movies like that, you expect them to just be a shoot ‘em up, but then they’re very smart, innovative and creative,” says Affleck when STACK meets with him and The Accountant director Gavin O’Connor in Los Angeles.“ This was the same – you look at it on the page, guy with a gun, shoot people, but then there’s some really interesting thematics running through it with fathers and parents and children and the way we try to protect them. Then with the autism, it’s really interesting because it has this kind of puzzle element and all this other stuff that you don’t expect, which transcend the ordinary genre aspects.”

After The Accountant topped the US box office it was hailed as Jason Bourne meets Rain Man, and O’Connor is the first to admit that Affleck wasn’t his first choice.

“When I started putting a list together, I honestly didn’t have Ben’s name on it because I heard he’d started doing Batman and he was going to direct a movie,” he says. “So he never crossed my mind, that’s the truth. Then his agent called and said, ‘what do you think about Ben?’ And I told them the same thing, it never crossed my mind, and then they said, well he’s got a window and we think you may like him for it. Then Ben and I got on the phone. I said to him, ‘Rain Man had Tom Cruise and we don’t have Tom Cruise so we’re going to have to figure this out to make it where there’s an accessibility’.“

Visiting autism schools and meeting with people on the spectrum, they soon discovered a pattern of common traits to utilise for Affleck’s character.

“What I consider most moving about the research I did, was not the differences of people who were on the autism spectrum, but how they were so similar,” recalls Affleck. “Everyone I talked to wanted to make friends and reach out and participate in the movie and make friends at their school. And some of them wanted to have romantic partners and some of them weren’t able to but still wanted to. That really moved me, that they have this basic fundamental human need to want to connect with one another and it was kind of heartbreaking to have something that was separating you from other people, and if you had that, you had to spend a lot of time of trying to circumvent that. He’s not the type of guy that doesn’t want to connect with other people, he wants very much to be able to connect with other people but he’s got hurdles and things which make it hard for him to do that.”

After Damon and Affleck won best original screenplay for their script about a math savant, Good Will Hunting, you’ve got to wonder if Affleck has a thing about numbers.

“To my surprise, the best part of my performance is the illusion that I’m good at math. It couldn’t be further from the truth. Gavin would just yell out numbers and I’d write them down.

“I‘m not good at math, not great at math. I already can’t do my daughter’s homework and she’s in fourth grade. I wouldn’t call on Matt Damon by the way,” he smiles.

“I’m gonna release my tax return when the time is right. There’s nothing to see. I’m not being audited.“

The Accountant is in cinemas from November 3.