Mathilda, a twelveyear old New York girl, is living an undesirable life among her halffamily. Her father stores drugs for twofaced 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 Leons apartment in the moment of highest need. Soon, she finds out about the strange neighbours unusual profession killing and desperately seeks his help in taking revenge for her little brother. Leon, 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...