Nicholas "Oz" Oseransky (MATTHEW PERRY) is a mild-mannered, but nervous and bumbling dentist who earlier survived discovering that his new next door neighbor, Jimmy "The Tulip" Tudeski (BRUCE WILLIS), was a former hit man targeted by a crime boss for death. Although the matter is behind them, Oz is fixated on security and has turned his home into a fortress where he hopes to raise a family with Cynthia (NATASHA HENSTRIDGE), who just so happens to be Jimmy's ex-wife.
When crime boss Lazlo Gogolak (KEVIN POLLAK) is released from prison and reunited with his son, Strabo (FRANK COLLISON), Oz's life quickly turns south again. The gangster's goons kidnap Cynthia and nearly kill Oz, sending him fleeing to Mexico where he hopes to get Jimmy's help in freeing his now pregnant wife. Yet, Jimmy has seemingly turned soft and seems distraught that he can't get Oz's former dental receptionist, Jill (AMANDA PEET), pregnant. She isn't happy with that or the fact that she isn't a very good contract killer.
Jimmy doesn't want to help Oz, but when Lazlo and his men arrive with their guns blazing, he, Jill and Oz quickly hit the road. After capturing Strabo, the threesome then sets out to arrange a hostage exchange with Lazlo, all while seemingly having something else up their sleeves at the same time.