When she sets sail for Lisbon, Catherine Laurence, a famous classical singer has but one wish: to be left alone. Unfortunately she soon gets bothered by a rude, invading man. Later she gets to know him better and becomes susceptible to his charm. She realizes that Michel is in love with her and it is not long before she goes beyond her disastrous first impression. Although not quite sure he is a perfectly honest man she entrusts him with a delicate assignment: keep her precious pearl necklace coveted by Van Coolart, a fake Dutch diamond-merchant, and give it back to her in Paris. If he is a robber himself, so much the worse for her. But if Michel keeps the Paris rendezvous love is in store for both of them. Nevertheless there is a crucial factor she regrettably disregards, composer Raymond Aubour, a faithful friend who has been her suitor for ten years.

Hector Dumontier has had enough of his wife Noémie : she is always immersed in those detective stories he disapproves of. To teach her a lesson, Dumontier decides to simulate the burglary of their house, with the help of an alleged jewel thief masked by a hood. He creates many false leads and everybody in the house gets suspected, from Ernestine, the maid, to Cabassol, the chauffeur, to Rosine, the Dumontiers'daughter. The disorder is complete and the various police detectives in charge do not help much.