Set in World War I, a young Scottish soldier, Private Plumpick (Alan Bates), of the carrier pigeon corp is sent to a French village to check on a message about a bomb that supposedly has been...

Set in World War I, a young Scottish soldier, Private Plumpick (Alan Bates), of the carrier pigeon corp is sent to a French village to check on a message about a bomb that supposedly has been left in the town. The reluctant Private arrives in the town only to be discovered by the Germans and takes refuge in the local insane asylum. When the Germans ask the inmates who they are each one answers with a different ludicrous name. When the Private is asked, he responds "I am the King Of Hearts". The ensuing response by the inmates is one of jubilation that the King has returned. Upon leaving the assylum, Plumpick leaves the gate unlocked and the rest is an allegory of madness and sanity gone topsy turvy, with Plumpick being crowned King and the inmates taking over the town. As the war rages in the town amidst love affairs and gaity, the question is raised, who is truly insane and who is not?