John Marcher is a civil servant who holds a deep-seated belief that a rare and potentially terrible fate awaits him. He refers to this impending event as the "Beast in the Jungle," an obsession that dominates his inner life and isolates him from genuine human connection. Believing he must remain unattached for when his destiny arrives, he relies on his careful facade of conventionality to hide his anxiety from society.

May Bartram is an observant woman who reunites with Marcher a decade after their initial encounter in Naples. She clearly recalls the existential secret he shared with her during their youth and agrees to watch for his anticipated fate. Following an inheritance, she purchases a house in London to stay near him. She acts as a stabilizing force in his life, helping him maintain the appearance of an ordinary gentleman to the outside world.