Hans Castorp is advised by his doctor to go to the mountains for a rest. Accordingly, he decides to visit his cousin, Joachim Ziemssen, a soldier by profession, who is a patient in the International Sanatorium Berghof at Davos-Platz in the mountains of Switzerland. He plans to stay there for three weeks and then return to his home in Hamburg. Hans has just passed his examinations and is now a qualified engineer; he is eager to get started in his career. His cousin’s cure at the sanatorium is almost complete. Hans thinks Joachim looks robust and well.

At the sanatorium, Hans soon discovers that the ordinary notions of time do not exist. Day follows day almost unchangingly. He meets the head of the institution, Dr. Behrens, as well as the other patients, who sit in particular groups at dinner. There are two Russian tables, for example, one of which is known to the patients as the bad Russian table. A couple who sits at that table has the room next to Hans. Through the thin partitions, he can hear them—even in the daytime—chase each other around the room. Hans is rather revolted, inasmuch as he can hear every detail of their lovemaking.

One patient interests Hans greatly, a merry Russian woman, supposedly married, named Clavdia Cauchat. Every time she comes into the dining room she bangs the door, which annoys Hans a great deal. Hans also meets the Italian Settembrini, a humanist writer and philosopher. Settembrini introduces him to a Jew, Naphta, who turns out to be a converted Jesuit and a cynical absolutist. Because the two men spend their time in endless discussions, Settembrini finally leaves the sanatorium to take rooms where Naphta lodges in the village.

From the very first day of his arrival, Hans feels feverish and a bit weak. His three weeks are almost up when he decides to take a physical examination, which reveals that he has tuberculosis. So he stays on as a patient. One day, defying orders, he goes out skiing and is caught in a snowstorm. The exposure aggravates his condition.

Hans’s interest in Clavdia is heightened when he learns that Dr. Behrens, who likes to dabble in art, has painted her picture. The doctor gives Hans an X-ray plate of Clavdia’s skeletal structure. Hans keeps the plate on the bureau in his room. Hans spends most of his free time with Joachim or with Settembrini and Naphta. The Italian and the Jesuit are given to all sorts of ideas, and Hans becomes involved in a multitude of philosophical discussions on the duration of time, God, politics, astronomy, and the nature of reality. Joachim, who is rather humorless and unimaginative, does not enjoy those talks, but Hans, since he himself has become a patient at the sanatorium, feels more at home and is not quite as attached to Joachim as he has been. Besides, it is Clavdia who interests him. On the occasion of a carnival, when some of the restrictions of the sanatorium are lifted, Hans tells her that he loves her. She thinks him foolish and refuses his proposal of marriage. The next day she leaves for Russia. Hans is in despair and becomes listless.

Joachim grows impatient with the progress of his cure when the doctor tells him that he is not yet well and will have to remain on the mountain for six more months. Wanting to rejoin his regiment, Joachim, in defiance of the doctor’s injunctions, leaves the sanatorium. The doctor tells Hans that he can leave, too; but Hans knows that the doctor was angry when he said it, and therefore he remains.

Before long Joachim returns, his condition now so serious that his mother is summoned to the sanatorium. He dies shortly afterward. Clavdia also returns. She has been writing to the doctor, and Hans has heard of her from time to time, but she does not return alone. She has found a protector, an old Dutchman named Mynheer Peeperkorn, an earthy, hedonistic planter from Java. Hans gets very friendly with Peeperkorn, who soon learns that the young engineer is in love with Clavdia. The discovery does not affect their friendship at all, and the friendship lasts until the Dutchman dies.

For a time, the guests amuse themselves with spiritualist séances. A young girl, a new arrival at the sanatorium, claims that she can summon anyone from the dead. Hans takes part in one meeting and asks that Joachim be called back from the dead. Dr. Krokowski, the psychologist at the sanatorium, is opposed to the séances and breaks up the sessions. Then Naphta and Settembrini get into an argument. A duel is arranged between the two dialecticians. When the time comes, the Italian says he will fire into the air. When he does so, Naphta becomes more furious than ever. Realizing that Settembrini will not shoot at him, Naphta turns the pistol on himself and pulls the trigger. He falls face downward in the snow and dies.

Hans had come to the sanatorium for a visit of three weeks. His stay lasted more than seven years. During that time he saw many deaths and many changes in the institution. He becomes an old patient, not just a visitor. The sanatorium is another home in the high, thin air of the mountaintop. For him time, as measured by minutes, or even years, no longer exists. Time belongs to the flat, busy world below.

An Austrian archduke is assassinated. Newspapers suddenly bring the world to the International Sanatorium Berghof, with news of war and troop movements. Some of the patients remain in neutral Switzerland. Others pack to return home. When Hans says goodbye to Settembrini, who is his best friend among the old patients, the disillusioned humanist weeps at their parting. Hans is going back to Germany to fight. Time, the tragic hour of his generation, has overtaken him at last, and the sanatorium is no longer his refuge. Dodging bullets and bombs in a frontline trench, he disappears into the smoky mists that hide the future of Europe.