Cathleen Calvert and her lover, crime scene investigator Patrick Kinsley, are weary of having to see each other on the sly. She will not divorce her husband, rich businessman Clifford Calvert, due to their prenuptial agreement. So the lovers scheme to get him out of the way by killing Howard Seltzer, an investment broker who is suing him, then framing Clifford for the murder. To do so, Patrick drives to Seltzer's house and tricks Seltzer into letting him inside by claiming that his car phone has died and that he has to make an urgent phone call. Patrick then shoots Seltzer and plants evidence to suggest that Clifford was responsible. Columbo's work is cut out for him, because Patrick is on the team handling the investigation. Final clue/twist: At a restaurant, Columbo sees Kingsley move the artificial sweetener towards Cathleen Calvert when they all receive coffee. A few minute later, Columbo sees Kinsley open the front door of a car for Cathleen Calvert instead of the back door. Columbo realizes that despite their claims otherwise, the two knew each other. If they had never met, as they claimed to Columbo, Kinsley would not have known that Cathleen prefers the front seat because she easily gets car sick when sitting in the back, or that she takes artificial sweetener with her coffee. A wedding photographer's shot of the Calvert couple dancing also helps reveal that the cat hair found on Clifford's suit jacket was planted by Cathleen, while an earlier photograph shows that Clifford did not have cat hair on his suit jacket prior to dancing with Cathleen. Directed by: Vincent McEveety. Story by: Charles Kipps.