Immer bei Vollmond (1970)

Whenever there is a full moon … the meek civil servant Christian Wegelin, tormented by his dark impulses and the very image of a humiliated, drab little mouse, strikes. In public, he is regarded as a respectable, inconspicuous citizen, but when the title’s full-moon moment arrives, he is driven to commit a crime. The small town is deeply disturbed by the attacks. Commissioner Mallet is tasked by his superior with finally putting a stop to the dangerous serial killer, who has already murdered so many women. Mallet is convinced that the unknown perpetrator must be a sex offender, since no other motive for the murders seems possible. At first, however, he can find no suspect who fits this description or whose behavior matches it. The killer, meanwhile, has all the classic traits of a henpecked man, oppressed at home by his wife and mother, and has consequently become a misogynistic psychopath weighed down by complexes. Mallet and his assistants pursue every lead. First, a petty crook and handbag thief in a leather jacket comes under suspicion, then the elderly, respectable grocer Stass, and finally a caretaker. A pimp also comes under the investigators’ scrutiny. Every lead proves false. When a middle-aged woman named Flora also falls victim to the criminal, Mallet and his team gradually begin to close in on the culprit.