M (1951) Joseph Losey - David Wayne, Howard Da Silva

A killer is preying on small children in Los Angeles. The police, under pressure from civic authorities, are conducting daily raids on the criminal world. This causes all illegal business to come to a standstill. In order to bring things back to normal, the top crime bosses hold a meeting and decide that as the unknown killer is the reason for the increased police vigilance, they will catch the killer themselves using their city-wide network of informants. If they succeed, not only will it bring them relief from the police raids but public, too, will hail them as good Samaritans. The plan is put into motion. Meanwhile, the police are combing the case files of people with a history of mental illness and commitment to psychiatric institutions in the past. And all this time, the killer is getting restless, getting the urge to kill again.