When a depressed and neurotic dentist, Nicholas 'Oz' Oseransky (Matthew Perry), living in Montreal realizes that he is living next door to a famous mob hitman, Jimmy 'The Tulip' Tudeski (Bruce Willis), his life turns upside down. His wife wants him to go to Chicago and try to turn Jimmy into the Gogolak crime family against whom testified, hoping to get a big reward from them. He goes but won't turn him in and ends up meeting Jimmy's wife and falling for her, which makes life next door to Jimmy all the more dangerous for Oz. Apparently Jimmy has no problem with fulfilling a hit, but infidelity in marriage is too much for him. While still in Chicago Oz is confronted by Frankie Figs (Michael Clarke Duncan) another hitman, and admits to knowing his whereabouts. He quickly returns in the hopes of getting away from the whole things, but finds that it won't be so easy to get away from Jimmy, and also must escape his wife's attempts at putting a hit on him. Will he survive 'The Whole Nine Yards'?