This great literate novel is the tale of Hans Castorp, the "delicate child of life" whom we first meet at age 23, ambivalently embarking on a career as a ship-building engineer in his home city of Hamburg, Germany. Before beginning his professional work, however, he journeys on what is intended to be a vacation and a pro forma visit to see his tubercular cousin, Joachim Ziemssen, at a sanatorium in the mountain town of Davos, Switzerland. Yet as the train pursues its course through the alpine scenery, Hans and the reader become aware that this is no ordinary journey. The impressionable Hans is transported away from the life and obligations he has known, to the rarefied mountain environment and insular community of the sanatorium.

At first uneasy, he soon becomes fascinated with and drawn to the routine established for the "consumptives" and to the social scene which flourishes there. Ordinary life seems increasingly unreal to him; his perceptions are heightened and he becomes aware of his physical, spiritual, and emotional vulnerability, as well as of his own sexuality. He is greatly attracted to one of the patients, a married woman of Slavic background, Madame Clavdia Chauchat. She reminds him of a schoolboy to whom he had been strangely drawn as a child. The turmoil brought on by this romantic obsession seems even to be reflected in his physical state, which is unstable and feverish.

As his intended stay of three weeks nears its close, the director of the sanatorium advises Hans to stay on to recuperate from a heavy cold, which appears to reveal an underlying case of tuberculosis. Hans is almost relieved at this news, for it provides him with a reason for remaining near Madame Chauchat as well as the opportunity to continue intriguing, profound discussions and cogitation about illness, life, time, death, religion and world view initiated by another patient, Herr Settembrini.

Settembrini is an Italian man of letters and humanist who believes that reason and the intellect must and will prevail, in daily life as well as in world affairs. He is contemptuous of the foolish flirtations and empty talk in which most of the sanatorium inhabitants indulge, and warns Hans repeatedly of the dangers inherent in cutting off all ties to real life and responsibility.

Nevertheless, Hans remains at the sanatorium for seven years, freeing himself from the constraints and conventions of life "in the flatlands" and instead engaging in a prolonged "questioning of the universe." This questioning includes a critical flirtation with death, stunningly described in the chapter, "Snow." Hans does not return home until the outbreak of World War I, in which he fights and survives.