South-West England, 1812. England is at war with America and when two hundred and fifty American prisoners-of-war arrive at Dartmoor prison, it is already overcrowded with French prisoners. Among the newcomers is Lieutenant Pilgrim Penn, an American merchant seaman, who soon falls in love with a local girl at a market held inside the prison walls. The inmates fight amongst themselves, despite their common enemy and the Americans are a particularly troublesome group. When the governor's daughter becomes romantically involved with one of them, he orders his soldiers to open fire during a minor disturbance, even though the war has ended and personal revenge is suspected as his true motivation.