One Sunday morning an unnamed European town is invaded by a foreign military. The village’s twelve soldiers are at a competition organized by a storekeeper named Mr. Corell. This competition is in the woods outside of town, and by the time the troops realize what’s happened, it’s already too late—the enemy has overtaken the village. Still, several soldiers try to fight back, but they’re either killed or taken hostage. In the aftermath of the siege, the townspeople slowly learn that Mr. Corell has been working as an informant for the foreign military, and aided them as they prepared to conquer the village as part of their authoritarian government’s larger expansion throughout Europe.
As whispers circulate about Mr. Corell’s involvement, Mayor Orden prepares to receive the invaders’ military leader, Colonel Lanser. Madame Orden, his wife, fretfully trims his ear hairs while his confidante, the local historian and physician Doctor Winter, discusses the nature of the colonel’s imminent visit. Madame wonders if they should offer the colonel tea or wine, asking, “Didn’t people in the old days—the leaders, that is—compliment each other and take a glass of wine?” Doctor Winter confirms that this used to be the case, but Mayor Orden decides not to “compliment” Colonel Lanser when he arrives, explaining that the townspeople wouldn’t approve of such a gracious, accepting gesture to the enemy.
When Colonel Lanser arrives, he apologizes for the unpleasantness caused by the invasion. He presents himself rather sheepishly, telling the mayor that he respects him and that he sees the military occupation of the town as nothing more than a “business venture.” He then asks Orden to cooperate with him, insisting that invasions and occupations go more smoothly when the conquered leader sets a precedent of civility for his people to follow. In addition to informing Orden that the high-ranking military officials will take up residence in his—Orden’s—house, he asks the mayor whether or not the man intends to help the invaders govern the villagers. Orden evades the question, saying, “You won’t believe this, but it is true: authority is in the town. I don’t know how or why, but it so.” He then clarifies that he will not act against the villagers’ will.
Despite Mayor Orden’s unwillingness to cooperate with the invaders, he allows them to set up living quarters in his home, accommodating the strict and procedural Captain Loft, the reserved and literal-minded Major Hunter, the kindly Captain Bentick, and the naïve Lieutenants Prackle and Tonder, along with Colonel Lanser himself. The men come in and out of the house, trading patrol shifts and talking about their experiences in town. Lieutenant Tonder, for his part, expresses an early sense of optimism, saying that he might even settle in the town after the war is over, since the people seem pleasant. Meanwhile, Major Hunter spends the majority of his time designing a railroad system that runs from the town’s profitable coal mine to the waterfront. This project is central to the invaders’ mission and is the reason why Colonel Lanser told Mayor Orden that the occupation of the town is nothing but a “business venture,” since the soldiers have been given orders to extract and export the village’s coal.
One day, Captain Loft comes into the common room where Major Hunter is busy drawing his plans for the railroad. He complains that he’s just seen Captain Bentick patrolling without his helmet, which he finds improper because he believes all soldiers should “maintain a military standard, an alertness, and never vary from it.” Colonel Lanser then sends Loft to relieve Captain Bentick from his post overseeing the coal miners. On his way, Loft comes upon Alexander Morden, a miner who has worked himself into a rage about the forced labor to which the invading military is subjecting him. Alexander rushes toward Loft, but Captain Bentick intervenes, and the enraged miner drives a pickaxe into Bentick’s head.
When he hears Captain Bentick has been killed by a miner, Colonel Lanser tells Mayor Orden that Alex will have to be put to death. He explains to Orden that it would be best if this death sentence came from him, the mayor, since this would communicate to the townspeople that they should cooperate with the invaders. He tells Orden, “If you wish to save your people from hurt, you must help us to keep order.” Mayor Orden refuses to do this, pointing out that he doesn’t even have the legal right as mayor to sentence a citizen to death. Colonel Lanser makes several remarks implying that he understands and sympathizes with Orden’s dilemma, but when they finally hold the trial, he sentences Alexander to death by firing squad. Seconds after the young man is shot, however, somebody throws an unidentified object through the window of the mayor’s house, injuring Lieutenant Prackle and surprising the colonel. Colonel Lanser begins to understand that it will be harder than he thought to beat this population into submission.
In the following weeks, the invaders have trouble making progress on the railroad project. The tracks constantly break, and English forces occasionally drop bombs intended to destroy the mine. The townspeople bitterly resent the soldiers, treating them with intense scorn and often refusing to speak to or acknowledge them. This weighs heavily on Lieutenant Tonder, who originally hoped to establish meaningful relationships with the villagers. Despite his fantasy, relations between the soldiers and the town continue to worsen, and the soldiers find that they must remain vigilant at all times or else risk getting killed. This deeply troubles Tonder, who quickly becomes disillusioned. At one point, he challenges Captain Loft and Lieutenant Prackle by asking them if they think the town is really conquered. The two men resent Tonder’s pessimism, but he presses on, likening the military effort to “flies” that “conquer the flypaper.” Prackle begs for him to stop speaking this way until, eventually, Loft steps in and slaps Tonder clean across the face, saying “Stop it, Lieutenant! Do you hear me?”
One night long after the town’s curfew, Mayor Orden’s cook, Annie, sneaks past the patrolling guards and visits Molly Morden’s house. Molly, who was married to Alex Morden before he was executed, lets her in and asks why she’s come. Annie tells her that the Mayor will be coming to her house that night because he needs a safe place to speak with two fishermen, Will and Tom Anders. Apparently, the fishermen’s brother, Jack, has been killed by the invaders for destroying one of their cars, and now the military is searching for Will and Tom, who plan to steal Mr. Corell’s boat and set off that night for England. Having confirmed that Molly’s house is free of danger, Annie sets off again to tell the mayor the coast is clear. However, just after Annie leaves, Lieutenant Tonder knocks on Molly’s door and asks to be let in. Once inside, he tells her that he’s seen her about town and that he’s lonely and just wants to talk to her. She realizes he doesn’t recognize her, despite the fact that he commanded the firing squad that killed her husband. In order to get him to leave, she tells him she’ll talk with him for a little while, but that he has to leave and come back another time. Finally, he agrees to do so, and takes his leave.
Not long after Lieutenant Tonder exits Molly’s house, Annie returns with the mayor, Doctor Winter, and the Anders brothers. The Mayor tells the two brothers that he needs their help: when they reach England, they are to tell English officials about the town’s invasion and ask them to send explosives. These explosives, Mayor Orden explains with Doctor Winter’s help, will enable the villagers to blow up the invaders’ railroad and defend themselves against the military. The two brothers agree to this plan. Suddenly, there is a knock at the door, and Molly quickly ushers everybody out the back entrance. On his way, Orden says, “Molly, if you’re in trouble, let us help you,” to which she replies, “The trouble I’m in no one can help me with.” When the room has completely emptied, she picks up a large pair of scissors and hides them inside her dress before saying, in a sweet voice, “I’m coming, Lieutenant, I’m coming!” When Lieutenant Tonder enters, she stabs him to death before fleeing the town.
Shortly thereafter, a plane flies over the town and drops countless blue packages, which scatter throughout the village. As the invaders make haste to analyze what these packages hold, the townspeople scurry about collecting them. By the time Major Hunter identifies the packages as containing small but effective bundles of dynamite, the villagers have already collected a great many them. Inside, there are instructions about how to properly use the dynamite, including a step-by-step procedure outlining the best way to blow up the railroad. Colonel Lanser frets over this new development, realizing how quickly he is losing control over the situation. To make matters worse, he discovers that Corell has gone over his head by writing to the government and obtaining official permission to play a more instrumental role in the town’s proceedings. As such, Corell advises Lanser to arrest Mayor Orden and Doctor Winter in the hopes of pacifying the townspeople. Lanser begrudgingly follows this advice, taking both men into custody and telling Orden that if he doesn’t urge his people to not use the dynamite, he will be killed.
In a conversation with Doctor Winter after they’ve both been arrested, Mayor Orden tries to remember the speeches Socrates delivered before he was put to death. As he fumbles through the lines, Colonel Lanser enters the room and listens eagerly, clearly sympathizing with this man whom he respects and for whom he feels sorry. When Orden finishes, Lanser tries to convince him to urge his people not to use the dynamite, implying that if the mayor would simply try to stop the destruction, Lanser might be able to spare his life. But Mayor Orden remains steadfast in his conviction that the people must do as they see fit. In the distance, two explosions sound, and Orden stands stiffly before revealing a small smile. On his way toward the door—and, presumably, toward his own death—he turns to Doctor Winter and quotes Socrates’ last words to his friend: “Crito, I owe a cock to Asclepius. Will you remember to pay the debt?” Doctor Winter lightly shuts his eyes, pausing before saying, “The debt shall be paid.”