Dr. Ray Flemming (Gene Barry) is a psychologist with a wealthy wife (Nina Foch). One night, at the couple's anniversary party, Ray receives a call from his patient and mistress, Joan (Katherine Justice). Ray's wife suspects that the two are having an affair and threatens to divorce him. Ray and Joan conspire to kill Ray's wife, with Joan providing the alibi. The pair are sure they've gotten away with their crime until Lt. Columbo (Peter Falk) starts sniffing around.