On returning home from a shopping trip, twelve-year old Mathilda (Natalie Portman) finds that her family havebeen slaughtered by a psychotic, drug dealing police officer (Gary Oldman). Fearing for her life, she takes refuge with her mysterious and solitary neighbour (Jean Reno). His name is Leon and he's one of the world's deadliest assassins. And while Mathilda begins to teach him how to live, Leon begins to teach her how to kill.