In a novel of formation set before the Great War, the young Hans Castorp, from Hamburg, climbs to Davos-Platz for a three-week visit to his cousin Joachim Ziemssen, who is being treated at the Berghof Sanatorium. Orphaned since boyhood, raised first by his grandfather, Senator Hans Lorenz Castorp, and then by his great-uncle Tienappel, Hans has finished his naval engineering exams and faces a career to which he does not know how to answer "For what?" In Davos, everything his cousin tells him (the dead carried down on sleds, the "psychic dissection" of the assistant Dr. Krokowski, the tedium of the six-month stay) provokes nervous laughter in him, and his first night in room 34 already announces that time there runs differently.
In the first days, Hans gets to know the world of the sanatorium: the lavish and abundant meals, the rest lying down on the balcony, the seven-minute thermometer, the little blue glass bottle that most carry in their pockets, and those who die without fuss. He also meets the Italian humanist Lodovico Settembrini, with his elegant speech and threadbare clothes, who holds forth on humanism and suggests he leave on the next day's train, and he sees enter the dining room, slamming the glass door, the Russian woman Clavdia Chauchat. A solitary walk ends in a nosebleed and a childhood memory: his schoolmate Pribislav Hippe, with Kirghiz eyes, had lent him a red pencil, and Hans realizes that Clavdia has the same eyes. In the third week, a cold that Dr. Behrens does not accept as a cold brings him to the office, where the doctor declares him "clandestinely one of us" and sends him to bed. Hans writes to his uncles that he will stay a little longer, and does not leave again.
Winter and Walpurgis Night
The following months turn the visitor into a patient. In a radiology room, in the dim light, Hans sees Joachim's heart and then his own hand. Hans falls in love with Clavdia and begins to imitate her manners, while Settembrini warns him that illness and despair are forms of licentiousness. In Dr. Behrens's home, before the oil portrait of Clavdia, he hears that the body is water and protein and that living is a combustion. Hans reads alone on the balcony books of anatomy and physiology to learn what life is. When the Austrian aristocrat dies, he goes to see the body and begins to visit the dying of the sanatorium. On Shrove Tuesday, Walpurgis Night, he asks Clavdia for a pencil, speaks with her alone in French and declares his love to her on his knees. She calls him a bourgeois and announces that she leaves the next day for Daghestan.
Naphta and the Death of Joachim
With Clavdia gone, Hans spends the spring and summer with botany and the stars, and meets the Jesuit Leo Naphta, Settembrini's neighbor, who has moved into the house of the tailor Lukacek. In front of him the two stage the great discussions of the book: science and faith, State and Church, reason and terror. Joachim, tired of the illness, is discharged and returns to his regiment, and Uncle James Tienappel comes to fetch Hans and gives up, disoriented. In the second winter, Hans buys skis, is caught by a snowstorm and falls asleep in it, dreaming. Joachim falls ill again, returns to Davos with his mother, is found to have tuberculosis of the larynx and dies one November night.
Peeperkorn and the Great Boredom
Clavdia reappears in the company of the Dutch planter Pieter Peeperkorn, of immense presence and sentences that almost never reach their end. Hans, fascinated and embarrassed, is called brother by him and seals a wine alliance, although Clavdia had kissed him one night in the vestibule. On a coach excursion to the Flüela valley waterfall, Peeperkorn makes a silent speech before the roar of the water and, the next dawn, kills himself. Clavdia leaves, and Hans feels the world off its hinges. Behrens calls him blasé; the narrator names what dominates him: the great boredom.
Hans spends the nights listening to records on the new gramophone. After a session with the glass in Hermine Kleefeld's room, Hans keeps his distance, until he agrees to attend a session of Krokowski's in order to call Joachim. With Valentin's Prayer playing in the background, the cousin's figure appears, and Hans asks forgiveness, turns on the light, demands the key from Krokowski and leaves the room. Meanwhile, the hatred between Naphta and Settembrini grows until the duel: one morning in the snow, Settembrini fires into the air, Naphta calls him a coward and shoots himself in the head.
The Thunder
The book speeds up. Old Consul Tienappel dies on the plain, the war breaks out, and Hans Castorp, who came for three weeks, goes down from the mountain to the battlefield. The last scene shows him advancing through the mud, softly singing a stanza of "The Linden Tree," until the narrator loses sight of him without saying whether he survives, and closes the book with a question: whether from this world festival of death love will still arise.