How to Kill 400 Duponts (1967)

The French Riviera is plagued by the criminal phenomenon Dorellik with his satanic laughter and the French police call Scotland Yard for help in the person of Commissioner Green. Dorellik is, however, financially in dire straits, so much so that he is abandoned by the secretary. He then looks for work with an ad in a newspaper and finds it: he is commissioned by Rafael Dupont to kill all the other Dupont of France in order to be the only heir to a Brazilian billionaire. Dorellik begins his work alongside the attempt to recapture the secretary.