In this ponderous French mystery-drama, based on an Ellery Queen story, blackmail would seem to be the least of the problems of Charles (Anthony Perkins). His adoptive father Theo (Orson Welles) has a madwoman for a mother, and a gorgeous woman of Charles' age (Marlene Jobert) for a wife. In fact, Charles is deeply attracted to her. In addition, his father encourages the whole family to dress in '20s clothing, which makes them all feel out of place. However, when he wakes in a strange bed with blood on his hands and no memory of anything the night before, he gets a little bit frantic. He calls Paul, his old professor of philosophy (Michel Piccoli), one of the few non-family members he can trust for discreet help. Theo has made his country estate into an eerily independent universe, not like anyplace else. Paul accompanies Charles to the father's strange home, and uses his philosophical training to try to solve the mystery of the bloody hands.