A week before the wedding of Chad Edwards and Sarah Leter, Chadís brother Rory Edwards breaks into Chad's house to acquire Chad's little black book for a bachelor party. Unbeknownst to him at the other side of the house an actual burglar, Nick, a ruthless psychopath, is breaking in. Nick discovers Rory and concludes he is a competitor theif and hides in a closet. While Rory is searching, Chad returns home early from his softball game and hears noise in his bedroom. When Chad enters the bedroom, Nick fatally shoots Chad then knocks Rory unconscious and taking him hostage. Nick leaves clues to frame Rory for the murder.
Nick's partner in crime is Ratty, the getaway driver. Ratty is a mildly retarded sociopath who works part time in a jewelry store. Nick doles out Ratty's medication to keep him tranquil and in control.; Ratty resents this. Ratty and Nick chain Rory in the basement of their house while they decide how best to frame him. While hostage, Rory psychoanalizes Ratty, befriends him and soon outwits Ratty and escapes. Because of evidence at the scene, the police believe that Rory killed his brother.
Two detectives, Terrance Kelly, young and energetic, and Jack Kruger, a month from retirement, are assigned to investigate. They disagree on Roryís alleged guilt.
After surviving two personal tragedies, Sarah has finally met the man of her dreams in Chad. She is devastated when she learns of Chad's death and attempts suicide.
Rory returns to his apartment for belongings, but finds Chadís murder weapon and the police converging on him. After narrowly escaping the police, Rory visits Sarah who is
recovering at home. Sarah corners Rory at knifepoint believing he is Chadís killer. After being convinced he is not the killer, Sarah unites with Rory.
Rory attempts to surrender himself to police but an overworked apathetic clerk wonít allow it. Rory and Sarah travel to the Nick and Rattyís getaway house for clues. Nick and Ratty have left. The police arrive and Rory instinctively runs to avoid capture. Meanwhile, Nick and Ratty seek the advice of an old boozer lawyer.
Sarah finds Rory in the garage of Chadís house and they share a bottle of whiskey. Overcome with hate and skeptical of the police, Sarah decides to track down Nick and Ratty and murder them to affect revenge. At the funeral of Chad, Rory becomes convinced it is his duty also to find and execute Nick and Ratty. Sarah and Rory use their intellect to sift through medical records and learn Ratty's true identity. They follow Ratty to discover Nick and Ratty's new hideout. Rory and Sarah are finally faced with the ultimate decision of whether they can truly pull the tirigger. Rory uses his psychological skills to craft a satisfying surprise ending.