Butch (Josh Hartnett) and Lee (Aaron Eckhart) are both boxing champions. Lee is called "Mr. Fire" and Butch is called "Mr. Ice". Lee is in the police enforcement team, while Butch is in a bad state. In a boxing match held by the police station, Butch deliberately lost to Lee, and joined the police station and became Lee's partner. The two became good friends who could talk about anything. The two were ordered to investigate a serial murder case committed by a guy named Nash. In an ambush, Lee shot a suspect who was under surveillance in order to save Butch, but failed to catch Nash. Later, the two found the body of Short, known as the "Black Dahlia", near the scene. Short died of a horrible cause. Lee soon gave up investigating the Nash case and concentrated on investigating Short's case alone. Bobby, a bank robber who was captured by Lee that year, was released from prison early, which also made Lee feel overwhelmed. In order to help his partner, Butch began to investigate on his own. However, as the investigation deepened and the truth gradually surfaced, he discovered the unknown secret behind Lee.