A professional assassin rescues a teenage girl whose parents were killed in a police raid.
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 Stanfield. Only her little brother keeps Mathilda from breaking apart. One day, Stanfield 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 Léon'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. Léon, who is completely unexperienced in fatherly tasks, and in friendships, does his best to keep Mathilda out of trouble - unuccessfully. Now, the conflict between a killer, who slowly discover his abilities to live, to feel, to love and a corrupt police officer...

The story takes place in the New York Mets , by Jean Reno hitman leon , played by the restaurant owner commissioned the murder . When he is the killer's identity appears calm and mysterious murder techniques makes the blood boil . But when he remove the killer mask , then return to become the ordinary man in the street , simple to have a basic identity card , bank account every day for at least a cup of milk , like watering and carefully wipe the beloved pot leaves, has a dual identity role-playing . Leon apartment , it was to steal the drug trade, police anti-narcotics group disguised gangster , seizing drugs and invasion , kill drug traffickers a missing little girl Ma Dida . Ma Dida hid next to Li Ang home for safety reasons , she accidentally discovered Leon identity of the killer in order to protect themselves and report Daughter Qiu , Madi Da Li Ang training she became a bona fide occupational requirements in a firm voice killer ... in the meantime , the police also fully search Ma Dida and detained . leon alone broke into the police station slaughter , police big panic I ordered the siege building and fully raid Li Ang , the two sides at war under the triggered an exciting final kill . Leon has been 40 years old , he was a professional killer, a habit loner and always abide by the principles do not kill women and children ; Matilda was just an ordinary 12-year-old girl next door . This person's life trajectory unrelated to the original would not be any intersection , however, simply because the latter unfortunately tragic Daughter of a disaster that makes two accidents came together , and between them produced a wonderful chemical reaction : love .