In a World War II–era internment camp in Scotland, presiding officer Maj. Perry (Ian Hendry) suspects that the imprisoned Nazi soldiers he monitors are plotting a large-scale prison break. But after Perry fails to figure things out himself, eccentric Irishman Capt. Connor (Brian Keith) is brought in to do some detective work. Before long Connor traces the plan back to the German Capt. Schlueter (Helmut Griem), leading to a man-to-man battle of wills and intellects.