With great excitement and morbid curiosity, New York high society prepares to receive Monsieur Tibault, a foreign composer endowed with a tail. After some speculative deliberation, the New York elite conclude that M. Tibault's tail is a vestige of evolution, like the appendix. Society's other distinguished visitor that season is the exquisite Princess Vivrakanard of Siam, with whom Tommy Brooks — a "pleasant, normal" young man — is in love. She is merely "tolerant" towards him. though more tolerant than she is with other wistful suitors. Tommy attends the distinguished composer's concert with the Princess and witnesses her body tense up when M. Thibault takes the stage. His jealousy only grows as he watches the two get on well at various social engagements; they utter few words to each other but seem to be kindred spirits. Tommy reflects: "It was as if that couple were foreign, indeed — not only to New York but to all common humanity. As if they were polite guests from a different star." A strange suspicion suddenly occurs to him: What if M. Tibault and the Princess are both cats? Various things confirm this theory, to his mind: a flash of fur through the composer's torn socking, the Princess's feline eyes, etc. Tommy's theory does not detract from his attraction to the Princess. Indeed, he asserts that he'd still marry her if she "turned into a dragon every Wednesday." So he seeks the help of a friend, Billy Strange, to get rid of M. Tibault. Billy presents him with a tale "embodied in the folklore of every land . . . the story of the traveller who saw within a ruined abbey, a procession of cats, lowering into a grave a little coffin with a crown upon it...he could not forbear relating to a friend the wonder he had seen. Scarcely had the tale been told when his friend's cat...sprang to its feet, cried out, 'Then I am the King of the Cats!' and disappeared in a flash up the chimney." Billy proposes that Tommy relay this tale at a dinner party with M. Thibault present. If the composer is indeed a cat, the story should compel him to declare his kingship and disappear. Tommy arrives at the dinner party, where he rehearses his lines in his head. He is interrupted by a guest who informs him that the Princess and M. Thibault are engaged as of that very day. Furious, Tommy re-commits to his plan, and it works. Upon hearing Tommy's fabricated tale, M. Tibault announces that he is king of the cats and disappears from the dinner party in a flash of smoke. After the fact, the guests posit varied explanations about what exactly transpired. No one can agree. The incident disturbs the Princess, who leaves for a ship voyage, never to be seen again; just like M. Tibault. Years later, married to another woman, Tommy suspects that the Princess and the conductor are reunited and reign together as the king and queen of the cats.