The Night Affair(1958)

Original title: Le Désordre et la Nuit

Vallois, a vice inspector for the Paris police, takes special interest in the plight of drug-addicted Lucky (Najda Tiller), whom he considers to be more victim than criminal. Taking it upon himself to wean Lucky away from narcotics, Vallois also wins her love -- and, incidentally, smashes the dope ring responsible for her addiction.