Mr. Crime is a mysterious and enigmatic character, described as a ghostly figure who follows and observes criminals, encouraging them to commit acts of evil. He acts as a devil on their shoulder, pushing them towards violence and crime. Despite his influence on the story, no one in the story can see or directly interact with Mr. Crime, and his origin and true nature are never revealed. The reader is the only one aware of his presence and influence, making him a powerful and intriguing character.