On 9 May 1940 the happy-go-lucky Captain James Barron, serving as an intelligence officer in Flanders, attends the wedding of the daughter of de Gruchy, a prosperous French wine merchant, in the city of Chartres. But when he awakes the next morning he learns that the German army has crossed the frontier. He soon finds himself in charge of several agents in France, a task rendered all the more difficult because James has fallen hopelessly in love.... Back in England he liases with many French agents, including the de Gruchy's, a situation complicated by his affection for their daughter, Liane.