As always for the intrepid bookseller-by-day, burglar-by-night, a simple job leads to bigger things.

First up, Bernie the bookseller is asked by a Manhattan collector to appraise his impressive library. He does so, and while in the apartment building, makes off with a terrific cache of rare stamps. Then, upon returning home he finds best friend Carolyn Kaiser in tears. Her beloved cat has been abducted, and the ransom is a painting by Mondrian, currently on display in a museum and nearly impossible to steal. Nearly. But then Bernie remembers seeing another Mondrian hanging somewhere...in the book collector's apartment. Before too long, the painting is gone, a body turns up and the police are knocking on Bernie's door. Guess who their number one suspect is?