Near the end of World War I, Scottish soldier Private Plumpick (Alan Bates) is sent on a mission to a village in the French countryside to disarm a bomb set by the retreating German army. He encounters a strange town, occupied by the former residents of the local psychiatric hospital, who escaped after the villagers deserted. Assuming roles like Bishop, Duke, barber and circus ringmaster, they warmly accept the visitor as their King of Hearts. With his reconnaissance and bomb-defusing mission looming, Plumpick starts to prefer the acceptance of the eccentric locals over the insanity of the war raging outside.
