During the Second World War, on territory occupied by the German army, a stranger arrives at the gates of a hospital for the mentally disabled. When he is taken to a doctor, he tells him that the purpose of his visit is to find an English spy who is hiding among the patients. The man is, in fact, a Gestapo officer called Windisch and he is to carry out his task before the Soviet army pushes its way towards this isolated house in the middle of the woods. The doctor tries to be of assistance and Windisch soon narrows his list of suspects down to three people: a former publisher of a literary magazine, an army sergeant and a man who thinks he is the Führer himself. He is also suspicious of a young woman who is acting strangely. Using simple provocation, Windisch tries to force the spy to give himself up, but the impaired logic of those around him gradually undermines his plans. He is still feeling increasing pressure from above, however, and he has to take drastic measures in order to force the spy out into the open. The director uses the entire situation for a critical analysis of the relationship between power and guilt, and fixed ideas and free will in a totalitarian state. The film was made in 1968.