A Police Officer Without Importance (1973)

Original title: Un officier de police sans importance

Camille, Dov and Joëlle live on the edge of society and are involved in petty theft helping them to buy their drug doses and to survive as best they can. One day, while attempting to rob a movie theater, they activate the alarm signal and it is Pierre, Camille's brother, who is doing a heist in the same building, who is arrested red-handed. The three young people decide to kidnap a police officer and exchange him for Pierre.