In the sixth and final Thin Man whodunit, Nick (William Powell) and Nora Charles (Myrna Loy) look into the mysterious killing of bandleader Tommy Drake (Phillip Reed). The police quickly hone in on the owner of a gambling ship, Phil Brant (Bruce Cowling), who was about to lose Drake's band to a competitor. Also among the many and varied suspects are: Phil's new wife, socialite Janet Thayar (Jayne Meadows); the band's voluptuous vocalist, Fran Page (Gloria Grahame); and the troubled clarinetist, Buddy Hollis (Don Taylor). With the assistance of jive-talking "Clinker" Krause (Keenan Wynn) and the clever terrier Asta, Nick and Nora are soon able to gather all the suspects at the reopening of the floating gaming establishment. In between the skullduggery and the usual wisecracks, Gloria Grahame performs a sultry version of Herb Magidson and Ben Oakland's "You're Not So Easy to Forget."