Nick Franco is a suave Italian womanizer who is carrying on simultaneous affairs with wealthy socialite Lauren Stanton and another mysterious woman named Lisa Martin. Stanton and Martin are shown to be very close on some emotional level, and they both share a hatred of Franco and his unscrupulous, violent ways with women.
Together, they plot Franco's murder. They are waiting in Franco's apartment when he returns home late one night, and Stanton shoots him with a silenced gun. Wrapping his body in an electric blanket, they leave the scene and return separately two hours later. Stanton pretends she has lost her key to Franco's apartment and awakens the building supervisor to let her in. As the two are walking towards Franco's apartment, Martin fires a gun inside the apartment, then flees through the French windows. Stanton and the supervisor rush into the apartment to discover Franco's body, still warm, lying on the floor.
When Columbo begins his investigation, Stanton pretends to be falling in love with him in an attempt to distract him from the case. Columbo in turn pretends to respond to Stanton's advances, but of course is ruthlessly pursuing the killer.