Wayne Dobby (Robert De Niro) is an evidence-gathering expert at the Chicago Police Department. He specializes in taking photos at crime scenes to find clues to solving the case. He is shy and withdrawn, and he never has the heart to shoot. His weird behavior has earned him the ironic nickname "Mad Dog." One day, Wayne walks into a grocery store near his home and encounters a robbery. He accidentally saves Chicago's loan-sharking gang boss Frank Milo (Bill Murray). Frank was very impressed by Wayne's handling of the robbery on the spot, so he decided to become good friends with the shy Wayne. In order to repay his saving life, Frank gave Wayne the beautiful bartender Glori (Uma Thurman) in his night club as a "gift" and kept him at his disposal for a week. At first, Wayne was not interested at all in this "gift", but as the days passed, he found that he could not help but fall in love with Gloria...