Spies from several countries try to find out what secrets are hidden in the mind of a young amnesiac girl who has appeared in Paris.

During World War II a young Frenchmen sees his brother killed in Alsace by a German officer. He vows revenge on all Germans, but after the War he is conscripted into the French Army and sent to Indochina. There he meets his brother's killer under strange circumstances.

A dozen elegant people are gathered in a writer's desirable mansion. In the grand tradition of Agatha Christie, they all have something to hide.They begin a cruel game of truth, a game where you're not supposed to tell lies. As the questions become more and more intimate and precise, the tempers rise, while outside the storm is raging. Enter a hateful person (played by Paul Meurisse, the nasty headmaster in "Les Diaboliques") who seems to know a lot about them. Someone is murdered. Whodunit?