Armand de la Verne, a lieutenant in the French cavalry and a notorious seducer, undertakes a bet that he will “obtain the favours” of a woman selected secretly by lot, before his company departs for its summer manoeuvres in a month’s time. His target turns out to be Marie-Louise Rivière, a Parisian divorcée who runs a milliner’s shop, and who is also being courted by the serious and respectable Victor Duverger. Marie Louise’s growing attraction towards Armand is tempered by her discoveries about his reputation, while Armand’s calculated strategy becomes undermined by his genuine emotions. A subplot follows the parallel but simpler courtship of Armand’s friend and fellow officer Félix and Lucie, the young daughter of a photographer.