Leon (Jean Reno) is a lonely professional killer who is hired by someone. One day, the little girl Matilda (Natalie Portman) from the neighbor's house knocked on his door and asked him to temporarily avoid being killed. It turned out that the owner of the neighbor's house was an eyeliner of the police's drug enforcement team. He was punished by the evil police (Gary Oldman) to kill his whole family just because he embezzled a small bag of drugs. Matilda was rescued by Leon and survived, and stayed with Leon. Leon taught the little girl how to use a gun, and she taught Leon French. The relationship between the two became closer and they got along well. The girl wanted to take revenge, but was caught instead. Leon arrived in time and rescued the girl. The battle between good and evil, mixed with resentment and hatred, gradually escalated, and greater conflicts were inevitable...