One of Alfred Hitchcock's great villains is Bruno, the sociopath from "Strangers on a Train." The actor, Robert Walker, was on the verge of a nervous breakdown. (Actually, he would die shortly after finishing the film.) Roger Ebert says Walker's real-world edginess colored his performance, in a good way. Bruno seems bright and charming, for a moment, but he is troubled. He sits too close to you. He says, "I'll let you read your book," then he keeps talking. He murmurs, "I always admire people who do things...." Of course, Bruno's greatest issue is that he believes murder is OK, and he offs a stranger in a crowded amusement park. (This is after an iconic moment when he gets irritated by a small child, and he pops that child's balloon with his cigar.) It seems clear that Bruno has no grasp on the consequences of his own actions, and there isn't a great deal of effort to explain "why" he is who he is. (Contrast this with th...