I read as many books about the psychology of a psychopath as I could and I researched what exactly happens to soldiers.

I'm not a method actor but it certainly does help to have that kind of dedication. I treated my preparation like I was in the military. I didn't go out ever. I went out for drinks probably twice in five months. I lived very monastically.

I had done a little bit one other time. This character [in Jack Reacher] is a psychopath, but I had been hired by Carlton Cuse and Randall Wallace.

I want to make sure everything has my 100%.

Psychopaths don't have that charming skill set. They definitely manipulate, but they do it through focused, unskilled means. They're more obsessive.

When I did Casual, I just let myself put on weight because he's a schoolteacher. He's not meant to be muscle-y.

You get a role like this in a big action movie [like Jack Reacher] and you can go one of two ways: you can paint in broad strokes, which happens a lot in action films, or you can get very detailed.