Detective Peter Smeth and his young and charming wife, Louise, visit Magasin Heiberg, where, at his wife's express request, he is to buy himself a new hat. He is not amused by the idea, but there is no getting out of it. Suddenly, however, an event occurs that causes the couple to change their minds. The daughter of the store's owner, Inge Heiberg, is found unconscious in the store's courtyard, and Peter and Louise rush to her aid. The fainting spell turns out to be shrouded in mystery.