Joyless is oppressed by a set of personal problems. He is an older man, a former widower who has married a second wife, a seventeen-year-old woman named Diana — toward whom he is deeply possessive and jealous, fearing her potential infidelity. His son Peregrine has from his youth been obsessed with the literature of travel and voyaging, an obsession that is now so strong that it dominates his life, even to the point of preventing him from consummating his three-year-old marriage to his wife Martha — a circumstance that has left her profoundly unhappy, and almost as psychologically disturbed as her husband. Blaze has a potential solution for all of the Joyless family's problems, in the treatments of a physician called Doctor Hughball, and the sponsorship of a mysterious nobleman named Letoy. Hughball had treated many disturbed Londoners successfully — even curing Blaze himself of his own suspicions of his wife's fidelity. His wife, Barbara Blaze, becomes an active participant in the eventual cure of the Joylesses, helping to manage Martha Joyless in particular. Letoy is a wealthy aristocrat who pursues an odd lifestyle: he dresses plainly, yet furnishes his servants in rich clothes — the opposite of what is standard for noblemen of Brome's era. He also keeps a troupe of players, who he and the Doctor employ in their treatment of psychologically distressed individuals. The Doctor administers a powerful sleeping potion to Peregrine Joyless, and together with Master Joyless and his wife Diana they go to Letoy's country estate. There, Peregrine is told upon waking that he has travelled to the Antipodes, the country directly opposite England on the other side of the globe. Letoy's players involve Peregrine in a pageant of life in "Anti-London," as a means of curing his obsession. In the process, Joyless and his wife are treated as well, unwittingly to them. Most of the play's middle and later portions are taken up by a play within a play, in which the Doctor, Blaze, and the actors, all under Letoy's direction, fool Peregrine into believing that he is actually in the Antipodes. The play goes anything but smoothly, as Martha attempts to interrupt, as Joyless and Diana comment caustically from the vantage point of their own unhappy marriage, and as Peregrine turns to whole enterprise his own way; the actors have to improvise and extemporize, and sometimes lose their way.