Martina is a 14-year-old adolescent who is growing up on the streets of a Rome suburb. She has a younger sister and her mother is a prostitute, her father is called Alì and has never acknowledged his paternity. Martina is also in the care of a young social worker. A slightly older boy called Sciù is in love with Martina but she refuses all contact because of her shyness but also her mother's chosen profession.
Martina and Sciù are nevertheless great friends and petty criminals. One day their petty thefts and tricks bring them to the attention of Fiammetta Saracina a young police officer who has managed to retain her humanity and defends the children even before her more severe and hardened superior officers.
Martina may be young but she is very determined and warns her mother that if she doesn't start looking after her little sister properly, she - Martina - will shoot Alì. Family is everything to Martina, though, as she realises the day Fiammetta asks her to become a police informant. Martina refuses and from that moment Fiammetta becomes her sworn enemy, determined as the policewoman is to respect the letter of the Law.