Handlung

During World War I, a British private, sent ahead to a French town to scout for enemy presence, is mistaken for a King by the colorful patients of an insane asylum.

During the latter part of World War I, Private Charles Plumpick is chosen to go into the French town of Marville and disconnect a bomb that the German Army has planted. However, Charles is chased by some Germans, and finds himself holed up at the local insane asylum, where the inmates are convinced that he is the "King of Hearts". Feeling obligated to help the inmates, Charles attempts to lead them out of town, but they are afraid to leave, and frolic about the streets in gay costumes.—Rick Gregory <rag.apa@email.apa.org>

An ornithologist, mistaken for an explosives expert, is sent alone into a small French town during World War I to investigate a garbled report from the resistance about a bomb which the departing Germans have set to blow up a weapons cache. He arrives to find a very eccentric group of townspeople, inmates of the local insane asylum, as it turns out, who have stepped into the characters of the fleeing villagers.—fyr

In November 1918 during the final days of World War I, the retreating German army marches out of Marville, the French town it had occupied during most of the war. A member of the French resistance learns that the Germans have planted a bomb somewhere in the town that will explode at midnight. He informs a nearby British regiment of this fact and alerts the Marville citizens, who immediately desert the town.

Colonel MacBibenbrook (Adolfo Celi) chooses the nonviolent poetry-reading Scotsman Private Charles Plumpick (Alan Bates) to go into Marville and disconnect the bomb. When Charles arrives in town, he is chased by the few remaining German soldiers and takes refuge in the local insane asylum. The inmates are convinced the Charles is the "Le Roi de Coeur" (King of Hearts) who has returned to them. Charles leaves the asylum but accidentally knocks himself out.

The inmates take advantage of the commotion to escape and circulate through the empty town, returning to their former professions. One is a barber (Michel Serrault), another is a former French army general (Pierre Brasseur), another is a bishop, another is a brothel madam (Micheline Presle); policemen mingle with soccer players. Two of the inmates known as The Duke (Jean-Claude Brialy) and the Dutchess (Francoise Christophe) spend the afternoon appreciating the wonders of nature. All of the inmates frolic about enjoying life.

Charles eventually wakes up. At first he doesn't realize that the townspeople he sees and interacts with are actually the same people from the asylum and he tries unsuccessfully to get them to help him find out where the bomb is. The townspeople/former asylum inmates have more important things on their minds, such as crowning him the King of Hearts.

Several German solders return to the town, but the loonies steal their tanks and chase them from the town. Several British Army Scotsmen arrive but are so unnerved by the strange sights they see... wild animals mingling with strangely dressed people... that they go back to the colonel.

Now that Charles is the King of Hearts, he feels obligated to protect these people for whom he fees tremendous affection. He tries to get them to follow him out of town, but they are too afraid to leave.

Charles meets and falls in love with Coquelicot (Genevieve Bujold), a virgin who works in Madame Eglantine's brothel. She has been assigned to provide the "king" with comfort. It is for her especially that he wants to find the bomb. But like the others, Coquelicot refuses to be afraid of the imminent explosion.

Charles figures out that the bomb is planted in the town clock. He climbs up the clock tower and prevents the explosion at the stoke of midnight. The loonies congratulate him and decide to celebrate for three years. Charles and Coquelicot are about to make love when the British army arrives. The colonel doesn't realize that it is the loonies who greet his troops, not the citizens of the town, and he happily allows his men to join in the festivities. He is attracted to Madame Eglantine.

The next morning, the regiment is about to pull out. Coquelicot is sad that Charles must leave town to go back to war. She and a few other escaped inmates pull him away from the others, tie him up and gag him. Charles and the inmates sit on a balcony as the men prepare to leave. Suddenly, a German regiment marches into town. The two armies fight each other in a climatic battle underneath the balcony and all of the soldiers on both sides are killed.

Just after the battle ends, the townspeople return to Marville. The inmates walk back to the asylum. Charles receives medals for bravery and the disarming of the bomb, but he is unhappy that he must return to fighting. He also misses his amusing and flaky friends from the asylum. In the final scene, Charles strips off all of his clothes and walks completely naked through the town to the asylum where he voluntarily enters and becomes one of them.