Beloved priest Father Thomasino is murdered in a San Francisco alley, and the police have few clues. But traffic cop Joe Martini becomes obsessed with finding the killer; he suspects Sylvio Malatesta. Ordered off the case, Joe turns in his badge and investigates alone. Soon he is a close friend of the Malatesta family, all delightful people, especially lovely cousin Anna. Uncertain whether Sylvio is guilty or innocent, Joe is now torn between old and new loyalties.

Soon after a Chinese princess comes to the US to buy planes for her people, she is murdered by a poison dart fired by an air rifle.