Asta, the dog from the popular Thin Man series, has vanished, and production for his next film is pending. MGM Studios offers a huge reward, and that's exactly what young private detectives Babs Norman and Guy Brandt need for their struggling business to survive. Celebrity dognapping is now a growing trend. When the police and city pound ridicule Basil Rathbone and ask, "Sherlock Holmes has lost his dog?" Basil also hires the B. Norman Agency to find his missing Cocker Spaniel.

The three concoct a plan for Basil to assume his on-screen persona and round up possible suspects, including Myrna Loy and William Powell; Dashiell Hammett, creator of The Thin Man; Nigel Bruce, Basil's on-screen Doctor Watson; Hollywood-newcomer, German philanthropist and film financier Countess Velma von Rache, and the top animal trainers in Tinseltown. Yet everyone will be in for a shock when the real reason behind the canine disappearances is even more sinister than imagined.