The Magic Mountain tells the story of Hans Castorp, a young engineer from Hamburg who goes to a sanatorium in the Swiss Alps to visit his cousin for three weeks, discovers that he is ill, and stays seven years, until the war, which the book calls the Great War, returns him to the plain.
In Chapter I, Hans Castorp arrives at the Berghof Sanatorium in Davos, where his cousin Joachim Ziemssen is a patient. Chapter II goes back to childhood: orphaned of father and mother, he also loses his grandfather. In Chapters III and IV, he meets the Italian humanist Settembrini, falls in love with Clavdia Chauchat, and, in the middle of the third week, the thermometer reads 37.6 and Dr. Behrens declares him "secretly, one of ours."
Chapter V shows his passage from visitor to resident: Hans Castorp sees his own hand in the X-ray, studies anatomy on his own, and on Walpurgis Night declares himself to Clavdia in French; she leaves the next day. In Chapter VI the Jesuit Naphta, Settembrini's adversary, enters, Hans Castorp nearly dies in a snowstorm, and Joachim, who had returned to the regiment, falls ill again and dies at the sanatorium.
In Chapter VII, Clavdia returns beside the Dutchman Peeperkorn, who ends up killing himself. The sanatorium sinks into boredom and irritation, Naphta kills himself in a duel with Settembrini, and finally the war breaks out. The book ends with Hans Castorp on the battlefield.