Does it take extraordinary ordinariness to play extreme madness and badness? That's the question that comes to mind as I listen to Willem Dafoe speak. Dressed in beige and grey, he sits on a sofa in a dimly lit Manhattan club and delivers quiet, circumspect answers to my questions. If this is a little surprising, it's only because the 59-year-old is one of the most captivating actors of his generation. He electrifies everything he's in, tempering wildness with the physical control of an actor meticulously trained in stage before screen.
It does his talents a disservice to speak only of his face, but it also happens to be one of the most remarkable in Hollywood, diabolic in one light, divine in another; he seems to have an almost supernatural ability for willing that cragginess into handsome or horrible, as the role demands.
In his latest movie, Anton Corbijn's subdued and subtle adaptation of the John le Carre thriller A Most Wanted Man, he's somewhere in between those two. He plays Tommy Brue, the head of a private bank, into which his late father has laundered an enormous sum of money for the most wanted man of the title, a mysterious half-Chechen, half-Russian illegal immigrant called Issa. That ill-gotten fortune moulders in the vaults while the question of Issa's identity - deadly terrorist seeking to fund attacks or torture-victim refugee wishing only to wash his hands of his father's dirty money? - steadily propels the film.
The movie has also granted Dafoe the strange, tragic privilege of sharing Philip Seymour Hoffman's last film. Hoffman plays Gunther Bachmann, a renegade counter-intelligence agent sinking ever further into professional - and personal - desperation. The actor died in February at the age of 46, a fact that makes his already devastating performance even more painful to watch.
"You know, emotionally it's very strange," says Dafoe. "I liked working with him very much. And I would have preferred to have done even more. Last time I saw the movie was in Sundance and Phil was alive then. I was happy to see him.
"He seemed ... you know, he was gregarious enough, he seemed fine. And then a couple of weeks later I heard the bad news when I was on the set of another movie. It stays with me. It adds a layer to watching the character. This guy that obviously has real conflict and real pain and it's natural to think of Philip and the circumstances of it. But I didn't know him well. The tragedy speaks for itself." Dafoe has always been guarded about his personal life and after he waves off a question about his childhood we talk a little about the irony of his profession: that a job all about being other people also entails this part, the bit where journalists want to scrutinise and reveal the "real" him. But, in his maddeningly equable way, he insists that he gets it.
"I'll be sitting in some doctor's office," he says, "and I'll pick up the RAGGIEST, JUNKIEST, gossipiest [magazine] - so I understand the impulse. Lou Reed used to say just lie, just make up stuff. And I haven't quite gotten there but one of these days I'm going to start. We're playing all these characters, but now I'm here as myself. Personality is an illusion, you know?" Dafoe has worked hard to elude typecasting but it's the mad and bad characters he'll be remembered for. The bilious writer snarling at his teenage cancer-patient fans in this year's The Fault in Our Stars, for example, or the depraved Bobby Peru, menacing Laura Dern in David Lynch's Wild at Heart with a mouthful of teeth like a bombed graveyard.
"What I'm always looking for," he says, "is the character who can allow me to lose myself. I think that's an exciting exercise. So naturally I gravitate towards things that are very far from me. And of course with madness - I don't know that I'm normal - but I would say I'm not mad and I'm not bad. On their own, I'm afraid of those things, but in a certain kind of structure, I'm able to really go to the thing with a certain gusto." Among his howlers is the deliciously bad pas de deux with Madonna that was 1993's "erotic thriller" Body of Evidence, with a soundtrack heavy on sleazy sax, and a plot even heavier on sleazier sex. Foremost among his highlights is his role in Oliver Stone's 1986 masterpiece Platoon. He shone as the quietly kind and brave Sergeant Elias, a beacon of human goodness within the moral rot of the Vietnam War, who also suffers one of the most memorably heroic deaths in film.
Dafoe occupies an unusual, if not unique, position in being an actor who can flirt with both high art and populist entertainment. "Sometimes the things that have the greatest pedigree and seem like the most artistic things turn into the pieces of shit," he says, "and the things that seem really junky and like guilty pleasure turn out to be very artful."
Who: Willem Dafoe
What: A Most Wanted Man, directed by Anton Corbijn
Where: At selected cinemas from today