Stephen enters the office of Mr. Stokes, the Head Butler of Tithe Hall, identifying himself as the new second footman. Mr. Stokes appears surprised and states that the house is not receiving any guests at the moment. Stephen produces a letter signed by Lettice Welt, the Viscount’s cousin, arranging his employment. Desperate after sleeping on a bench in Penzance with no return fare, Stephen watches Mr. Stokes read the letter while chaos can be heard in the corridors outside.

Stokes tells Stephen that Miss Lettice’s letter instructs him to hire Stephen without giving the Viscount details about Stephen’s past. Disapproving of this secrecy, Stokes questions Stephen about his history, and Stephen explains that the Borstal Society, a charitable organization that helps recently incarcerated young people find work once they’ve been released, has provided the livery for his work at Tithe Hall and instructed him to accept a beginner’s wage. When Mr. Stokes asks how he came to be detained in a Borstal Institution, Stephen faces the question he has been dreading.

Stephen delivers a rehearsed account of his time in juvenile detention, where he repented of his wrongdoing, paid for his mistake, and was fully rehabilitated. Mr. Stokes interrupts, noting that Lord Stockingham-Welt is exacting and has forbidden new arrivals under any circumstances. Just as Stephen despairs, Stokes reverses course, explaining that the house desperately needs workers who are strong, healthy, and resilient. He says he will hire Stephen, but he must first persuade the Viscount.

They move through the chaotic servants’ corridors filled with servants carrying oxygen tanks, stacked provisions, and other unusual items. Stephen observes boarded windows and sandbags and asks about the mysterious preparations. Mr. Stokes explains that successful servants must remain invisible, appearing only when required and speaking only when addressed. He firmly advises Stephen never to ask such questions again.

Mr. Stokes leads Stephen through frantic corridors and outlines his duties: He’s to polish boots, polish silverware, and eventually assist Stokes and Lowen, the first footman, with dinner service. Stokes adds that Stephen will also care for Miss Decima, the Viscount’s elderly great-aunt, who lives in the isolated Nursery and has exasperated all female staff.

Stokes explains that World’s End is the country’s largest tidal island, frequently cut off from the mainland when tides cover the causeway. Stephen admits he cannot swim. They enter a hidden servants’ staircase concealed in a cupboard—one of many secret passages built by the Viscount’s father, allowing staff to move unseen throughout the house. Emerging into an electrically lit grand hallway, Stokes demonstrates the butler’s mirrors: convex mirrors enabling staff to check around corners and avoid encountering the Viscount.

In the corridor, Stephen notices a suit of armor holding a crossbow loaded with a four-pronged bolt at the door of the Viscount’s study.

Mr. Stokes and Stephen enter the imposing study where Lord Stockingham-Welt stands by a fishbowl, annoyed by the interruption. He orders the entire household gathered in the drawing room at 10 o’clock before sealing the doors. Noticing Stephen, the Viscount grows angry and demands that Stokes remove him immediately.

Mr. Stokes calmly mentions they may need Stephen to manage Miss Decima. The Viscount’s anger dissipates into concern for his difficult great-aunt, and he reluctantly agrees to hire Stephen. When Stephen speaks out of turn to express gratitude, the Viscount detects his Bow accent and mocks his working-class origins. He boasts about his family’s aristocratic lineage, gesturing to the corridor armor and claiming its crossbow bolt killed King Harold at Hastings. The Viscount tells Stephen he is fortunate to serve such a family. Cryptically, he adds that tomorrow Stephen will discover just how fortunate. As a clock strikes 10, the Viscount orders everyone assembled in the drawing room.

Stephen goes to his small bedroom in the servants’ quarters to change into his livery, the footman’s uniform provided for him by the Borstal Society. While unpacking, he accidentally drops a framed photograph of his Nan, his only memento of her. Relieved that the frame is undamaged, he places it on the windowsill before rushing downstairs.

In the crowded drawing room, five guests sit: a glamorous older woman, a young boy, a large red-faced man, a bespectacled man, and a grim-looking man in a dark suit. The Viscount announces that tonight, Halley’s Comet will bring an end to the world as they know it when Earth passes through the cyanogen gas of the comet’s tail, which will make all the air on Earth fatally toxic to its human population. He introduces the bespectacled man as Professor Müller, a German colleague from the Cometary Cataclysm Society, who elaborates on the catastrophic consequences of the comet’s arrival, including massive tidal waves, giant hailstones, poisoned wells, and blinding electrical storms.

Stephen and the others in the room are dubious about the claims, and the man in the dark suit appears furious. The Viscount proclaims that Tithe Hall, protected by its cliffs and sealed against gas, is the only place prepared for disaster, and that as the sole survivors of the disaster and men of superior intellect and lineage, they will rebuild civilization in the wake of its collapse. He orders Stokes to mobilize the staff, announcing the world will end in seven hours.

In the servants’ hall, the staff erupts in protest. Mrs. Pearce, the housekeeper, confronts Stokes, who admits he knew nothing of the full plan. He explains they have six hours to make the East Wing airtight and seal everyone in their rooms overnight with food, water, and emergency oxygen tanks.

Lowen, the first footman, angrily protests the unfair dismissal of grounds staff. Stokes warns that if the Viscount is deemed unfit, control of the estate will pass to Edwin Welt—the man in the dark suit—who has long wanted to close Tithe Hall and eliminate their positions. They must prove their worth by executing the orders perfectly. Mrs. Pearce raises the problem of Miss Decima, who refuses to leave the Nursery. Stokes assigns Stephen to spend the night attending Miss Decima.

Stephen locates Lowen on the second floor. The angry footman slams him against a wall, threatening him for trying to take his job. Stephen notes that traditionally, taller footmen are paid more, and Lowen is much shorter than him. As Lowen storms off, Stephen notices Lowen’s shoes have small heels.

Stephen sees guests approaching in a butler’s mirror and stands rigidly against the wall to remain unnoticed as they pass. He overhears Edwin furiously complaining about the presence of a German in the house and the damage it could cause to his political career. Edwin reveals he agreed to the Viscount’s request that he visit World’s End, expecting a meeting about the inheritance. Jolyon, a former Rear Admiral in the British Navy, worries about boredom, while Lettice, the Viscount’s cousin, suggests leaving with her grandson Gilbert. Edwin forbids anyone from leaving the house to contain the family scandal, mentioning several past incidents that have caused the family embarrassment.

After the others move on, Stephen approaches Lettice to thank her for arranging his employment. She stares blankly, having no idea who he is. Mr. Stokes appears silently, pulls Stephen away, and scolds him for breaking his invisibility. Stephen realizes with certainty that Lettice did not arrange his hiring.

Stephen and Lowen spend the afternoon sealing fireplaces throughout the house, with Lowen deliberately making the work miserable for Stephen. The guests create additional difficulties—Professor Müller blocks corridors while documenting the day with his camera, Jolyon conscripts Lowen as his personal valet, and Lettice constantly demands tea and refreshments for Gilbert.

By half-past three, they finish the fireplaces and begin sealing guests into their rooms under the Viscount’s orders. Mr. Stokes plugs each keyhole with hot wax. The Viscount departs to prepare his own study, ordering Stokes to attend to the final preparations. Stokes tells Stephen to verify the maids’ rooms are secure before being taken to Miss Decima.

On the dark top floor, Stephen finds an unsealed door with light underneath and hears someone crying inside. He enters and recognizes Temperance, the weeping maid from that morning. They briefly connect over their shared London origins, and she warns him about Miss Decima. Stephen grows embarrassed when she notices his ears turning bright red and flees as Temperance seals herself inside her room.

Mr. Stokes leads Stephen through the dark, empty house to the Nursery, which is the only part of the house that lacks electricity. He provides tools, a tea tray with three knives, and instructions to seal the side-exit keyhole with wax. Since the Nursery has no staff bell, Stokes says he will retrieve Stephen in the morning.

Stephen enters the dilapidated, foul-smelling Nursery. In the hallway lie thrown objects—a meal, books, a paperweight, and a rhino horn. He finds Miss Decima’s bedroom covered floor-to-ceiling in handwritten papers. The elderly woman sits writing, wearing a nightgown with her false teeth on the desk. Startled by his arrival, she reinserts her teeth and demands her coat and hat, announcing they are going outside.

When Stephen protests that the comet is about to pass, Miss Decima dismisses it as an absurd stunt and reveals she orchestrated his hiring. She forged Lettice’s handwriting to request a reformed criminal from the Borstal Society, needing someone morally flexible to circumvent the lockdown and help her observe the comet. Stephen assists the frail woman into an old wicker wheelchair while she calmly explains why the comet’s gases are harmless and mocks him for believing the Viscount’s warnings. Stephen opens the side door to fresh sea air. Miss Decima playfully pretends to choke before laughing at him and ordering him to gather her equipment.

Stephen pushes the squeaking wheelchair through gardens and overgrown woods toward the sound of crashing waves. They reach a flat heath ending at a cliff edge, with the ocean stretching before them. After several adjustments, Miss Decima positions her telescope, and they wait for darkness.

As night falls, Stephen feels the day’s tension dissolve. The comet appears in the clear sky, brilliant, with two distinct tails—one white from dust, one blue from gas particles. Miss Decima lectures on its history and composition, explaining that it was formed billions of years ago and witnessed throughout human civilization. She notes that the comet has passed the sun, so its tail now leads its head.

Miss Decima instructs Stephen to transcribe her dictated observations into a notebook. He discovers he excels at the task and feels a surge of pride. They work together in peaceful equilibrium, with Miss Decima observing through the telescope while Stephen records her measurements.

Stephen struggles to push the wheelchair back up the hill. They return to the dark, silent house undetected. Exhausted, Miss Decima settles at her desk and asks for tea so she can write up her notes for the Royal Society. When Stephen reaches for a jar of tea leaves, she sharply orders him to use a different one. While making tea, he notices her feet are in terrible condition, cracked and purple.

Stephen’s mention of the Viscount’s scientific reputation triggers a profane tirade from Miss Decima. She claims the Viscount stole her research and denounces the entire Welt family as parasites who married into the noble Stockingham family for money. She laments that her brilliant scientific career was sacrificed in favor of men she considers mediocre, leaving her confined to these rotting rooms.

Stephen serves her tea and escapes to seal the Nursery doors. Deciding to speak with Mr. Stokes about Miss Decima’s deplorable living conditions, he retires to his own damp, dark room. He kneels for his nightly prayers but falls asleep mid-prayer before he can pray for the Viscount.

The comet passes by Earth as Tithe Hall remains silent in the deepest part of night. The narrator reveals that three people are not asleep. The first is Miss Decima, sitting alone in darkness and watching her bedroom door. The second is the Viscount, who is dead. The third is the man who watched him die.