When the valet of a German baron visiting Paris is stabbed to death, the murder is not allowed to interfere with the glittering social life of the Belle Epoque.

Inspector Gautier has scarcely begun to investigate the murder when he is instructed to make secret enquiries into a case of espionage involving the Minister for War. The minister has been wildly indiscreet, and Gautier's enquiries uncover a murderous conspiracy, which is brought to a denouement during a spectacular historical pageant under the shadow of the Eiffel Tower.