Based on

Movies like En plongée (1926)

The naval officer Maurice de Vergnes, tired of the extravagance of his fiancée Moussia, finds with pleasure a childhood friend: Anna. Jealous, Moussia breaks up with him and Maurice marries Anna. A few years later, Moussia reappears when war is declared. She is now a spy under the orders of Howell... This is a troncated version of a longer film.