Looking for Unknown Film - Please Help!

I've been searching for a long time for a film I saw about 40 years ago, but unfortunately I've forgotten the title. Perhaps someone here knows it based on the following description: Basic Information: - Time period: Presumably from the 1970s or 1980s (maybe older) - Origin: European film, probably French or Italian (definitely not American) - Cast: Essentially only two male main actors - Genre: Psychological thriller/drama with supernatural elements Plot: The movie mainly takes place in a house where a man lives alone. He receives a visit from a man he doesn't know. The visitor tells the owner of the house about a special group to which he belongs. Each member of this group has a different person to whom they wish evil. The special thing: All group members concentrate together on harming the respective target person through collective negative thinking - and this “thought power” is supposed to actually have an effect. The decisive twist: Throughout the conversation, the homeowner assumes that the visitor wants to recruit him as a new member of this group. The visitor explains in detail how the system works and cites examples from the past where people have been harmed by this collective mind power. But then the surprise: As soon as the homeowner starts to believe in the effectiveness of this method, the visitor reveals to him that he didn't want to recruit him at all. Instead, HE himself is the target - all the group members are already thinking about him and wishing him ill. Special features: - Very dialog-heavy film, mainly a chamber play between two people - Psychologically sophisticated twist as climax - Atmosphere presumably dark/spooky - Deals with themes such as mind power, collective manipulation and psychological terror Do any of you have an idea which movie it could be? Any advice would be very helpful! Many thanks in advance for your support!