Josh Hartnett has told RTÉ Entertainment that his role as the doting dad turned serial killer in M Night Shyamalan's Trap has been one of the highlights of his career.
The veteran actor, whose CV includes everything from The Virgin Suicides to Black Hawk Down to Penny Dreadful to Black Mirror to Oppenheimer and The Bear, is perfectly cast in the twist-filled thriller, billed as 'Purple Rain meets The Silence of the Lambs'.
Hartnett's character, Cooper, discovers that the pop concert he's attending with his daughter, Riley (Ariel Donoghue), is a sting operation to bring him to justice.
As the net closes in on Cooper aka The Butcher, he struggles to keep his everyday mask on - and Hartnett excels at showing the toll it takes on Cooper to appear normal as he scrambles to find an escape route.
"Night and I had a lot of conversations about the tone of the film and how we wanted that transition to take place," Hartnett told RTÉ Entertainment.
"So before we started, I kind of had a sense of where we were going to go with it. The main thing for me was to understand what this character becomes in the film and not what he pretends to be at the beginning.
"And so all of that stuff at the beginning is a facade, and when the facade starts to crack, it's very uncomfortable, because he's not used to letting it crack in front of people.
"That's the trick: he's been very good, as he says in the film, separating the two lives - and now he's forced to show his hand. The transition is an uneasy one, and I wanted to make it feel that way."
Hartnett said that making Trap had brought him and Shyamalan to some "uncomfortable" places.
"Uncomfortable meaning we had to do a lot of research on psychopathy and serial killers," he explained.
"We had to decide - and we did decide very early on - that we wanted this character to be psychologically intact throughout, so if you were to go back and rewatch, it's not us playing two different characters. We had to make sure that layer of kind of artifice at the beginning had a sort of artificial quality to it.
"In my opinion, there's a lot of over-the-top girl-dadding [by Cooper]. There's a lot of analysis he's doing with his daughter that feels maybe less like a dad would analyse his relationship with his daughter and more like problems that he could solve in order to make his daughter's runway a little bit clearer. He thinks of her reaction to him as a good indicator of how he's doing in his act, right?
"I mean, as far as the uncomfortable bits, there are obviously some uncomfortable bits within the film. It was important to highlight those, to make them as realistic and dark as possible, because you don't want to cheat the audience. You want them to understand who they're dealing with at the end of this film.
"I don't want to give anything else away, so I just want to kind of keep it as broad as possible, as vague as possible, at this point!"
Hartnett said that audiences who have seen Trap wanted two outcomes at the same time.
"They wanted to see him escape, but they also wanted him to get caught," he continued.
"Night is very good at feeling what the audience is going to feel, in a way I've never seen a director do it before. And so when we were watching the film with an audience for the first time, everything that he talked about back before we shot the film, what he wanted from the audience, was happening. And the way that they were responding to it was remarkable."
"I would love for you to see it with a big audience, because people's energy, you can feel it shifting from gentle titters to, like, very raucous sort of aggression to back to kind of cheering for him," Hartnett concluded.
"Feeling that weird ride that they go on is a remarkable achievement from a filmmaking standpoint, but also really gratifying from a performance standpoint as well, because I wanted it to be as engaging as possible. And hopefully, we achieved that."
Trap is in cinemas now.
