The Beast in the Jungle is the story of John Marcher, a man preoccupied with the idea that he will be slain in a dramatic fashion. This foreboding dominates his life, lying in wait in his subconscious like the eponymous beast, and causes him to squander the affections and attention of May Bartram. John does not realize that the calamity he spent so long anticipating was in fact his own inability to settle down and love May in return.
John Marcher, the protagonist, is reacquainted with May Bartram, a woman he knew ten years earlier, who remembers his odd secret: Marcher is seized with the belief that his life is to be defined by some catastrophic or spectacular event, lying in wait for him like a "beast in the jungle." May decides to buy a house in London with the money she inherited from a great aunt, and to spend her days with Marcher, curiously awaiting what fate has in store for him. Marcher is a hopeless egoist, who believes that he is precluded from marrying so that he does not subject his wife to his "spectacular fate".
He takes May to the theater and invites her to an occasional dinner, but does not allow her to get close to him. As he sits idly by and allows the best years of his life to pass, he takes May down as well, until the denouement where he learns that the great misfortune of his life was to throw it away, and to ignore the love of a good woman, based upon his preposterous sense of foreboding.