...An ordinary day at a Parisian notary office comes to a tragic end. Telephonist of notary Rochet, Mademoiselle Alice Postic, stays late at the office to chat with her friend on the phone and ends up finding her boss in death's throes, with a dagger in his back. After calling the police, Alice faints, but when the policeman arrives, it turns out that the corpse has disappeared! Arriving on call, the police inspector Granden turns out to be Alice's long-time acquaintance, but now he in every possible way disavows their love, which was once between him and Mademoiselle Postic. In connection with the murder an investigation begins and the notary together with his wife are the main suspects. But everything ends in the most ridiculous way: in the midst of interrogations, the "late" Rochet arrives in the office, who spent an evening at the opera!