The thing that makes this movie so powerful after eighty years is that Bogart never lets you forget how close Sam Spade is to losing control and becoming a killer for real. Spade is actually a stone cold psychopath, masquerading as a lonely man of integrity. Everyone senses it, even the people who hate him the most. Like the mean police lieutenant says, "You haven't heard me say you killed anyone. You're the one who keeps bringing that up."
