The castle of Villemaur is a tourist attraction. As the story begins, a guided visit is being conducted for some visitors. It is a well preserved building, but unknown to the casual eye, it harbors a Nazi war criminal that is trying to evade justice. The marquis of Villemaur gathers some former allies whose loyalties are with the evil force that caused so much harm during the war. Unknown to him, his own daughter is seeing a Russian, who is after one of the most sought after German.

Among the people that gather with the marquis, is Dromard, a man wearing a black monocle on his good eye. In fact Dromard has infiltrated the select group. He works closely with Commisaire Tourmire in their quest to apprehend this evil man. Dromard and his good friend Trochu will get involved in finding their man. Secret areas of the castle are perfect for the group in where to hide, but justice will prevail.

Georges Lautner directed the film, that seems to have been based on the character of Dromard, a suave detective-like man. Several films were based on the novels of Remy, adapted for the movies by Jacques Robert and Pierre Larroche. Paul Meurisse appears as the man with the monocle, as his disguise. Bertrand Blier is Tourmire. Jacques Marin, an actor whose presence appeared in many American films is good as Trochu. The lovely Elsa Andersen adds her beauty to the film.