Mathilda, a twelve-year old New York girl, is living an undesirable life among her half-family. Her father stores drugs for two-faced cop Norman Stansfield. Only her little brother keeps Mathilda from breaking apart. One day, Stansfield and his team take cruel revenge on her father for stretching the drugs a little, thus killing the whole family. Only Mathilda, who was out shopping, survives by finding shelter in LÃ©on's apartment in the moment of highest need. Soon, she finds out about the strange neighbour's unusual profession - killing - and desperately seeks his help in taking revenge for her little brother. LÃ©on, who is completely unexperienced in fatherly tasks, and in friendships, does his best to keep Mathilda out of trouble - unsuccessfully. Now, the conflict between a killer, who slowly discovers his abilities to live, to feel, to love and a corrupt police officer, who does anything in his might to get rid of an eye witness, arises to unmeasurable proportions - all for the sake of a little twelve-year old girl, who has nearly nothing to lose.