Plumpick is declared 'King of Hearts' by the lunatics and finds himself caught up in their lives while trying to find and defuse the bomb. What he finds in Marville are the inmates of the town's asylum, who take to the streets, houses, and shops and create their own eccentric community. Private Charles Plumpick, a gentle young Scotsman who cares only for poetry and his carrier pigeons, is sent to investigate. The townspeople get wind of this and flee in panic, alerting the Allied forces. In the latter days of World War I, German occupying forces retreat from the town of Marville, France, after planning to destroy the village with a secret bomb set to go off when the figure of a knight on the town's clock tower strikes the midnight gong. Discarding his uniform and equipment, he returns to the asylum, stands completely naked before a pair of startled nuns, and waits to be committed. Though Plumpick is assigned to another unit, he does not remain with it for more than a few minutes. Witnessing the senseless slaughter, the inmates voluntarily return to the relative sanity of the asylum. Only Plumpick survives the two forces' simultaneous fire. Marching on opposite sides of the town square, the two forces discover each other when a lunatic throws a flower down from a balcony. Hearing the explosions, the Germans return to the town to investigate. The town celebrates with the Scottish soldiers by exploding fireworks. Eventually a chance remark by Coquelicot leads Plumpick to the village clock, and he disconnects the bomb's detonator a few minutes before midnight. Ignoring Plumpick's frantic but futile search for the bomb, they devote their energies to preparing for a royal wedding between their newly-crowned king and a dainty acrobat, Coquelicot, a virgin taken from the lunatic whorehouse. A harmless and carefree lot, they crown Plumpick their King of Hearts, move into the houses and shops of the town, and assume the various roles of barber, bishop, duke and duchess, bordello proprietress, etc. By the time he arrives at the village, the only inhabitants remaining are the inmates of the insane asylum and the animals from the zoo.

A mildmannered private, Charles Plumpick, is chosen to investigate because he speaks French. As the villagers evacuate their town, one of them gets word of the bomb threat to a nearby Scottish regiment. The charge is triggered to explode when an armored knight on the church steeple clock strikes the hour of midnight with his mace. As World War I nears its end, a battalion of retreating Germans arranges for an entire French village to be blown up by placing an explosive in the town square.

King of hearts 4711