Set in early 20th-century Japan during a period of rapid modernization, the novel is narrated by a nameless stray cat who is taken in by a schoolteacher and proceeds to observe, with increasing philosophical sophistication, the absurdities of human society.
The cat recalls being born in a dark, damp place and handled roughly by a student boarder before being abandoned. Hungry and cold, the kitten crawls through a gap in a bamboo fence into a house where the servant woman, O-san, repeatedly throws him out. The master of the house, a schoolteacher named Sneaze, intervenes: "In that case, let it stay" (3). Though never given a name, the cat settles into the household and begins studying its inhabitants. Sneaze pretends to be hardworking but mostly naps in his study, has chronic dyspepsia, and dabbles in hobbies he never masters, including watercolor painting, violin, and Noh, a traditional Japanese performance art. His friend Waverhouse, a self-styled aesthete, tricks him into believing that the Italian painter Andrea del Sarto advocated sketching from nature, then confesses the advice was a complete fabrication, revealing his habit of bamboozling people with invented anecdotes.
The cat also befriends two neighborhood cats: Rickshaw Blacky, a tough cat belonging to a rickshaw-garage owner who complains that his master confiscates every rat he catches to collect a bounty, and Tortoiseshell, a beautiful cat belonging to the mistress of the two-stringed harp. Blacky's story of unrewarded labor solidifies the cat's resolve never to catch a rat. When Tortoiseshell later dies of a cold, the cat overhears her household blame him as a bad influence and resolves never to return.
At the New Year, the cat gains modest celebrity when admirers send postcards referencing him. A series of visitors enlivens the household. Coldmoon, a former pupil who has risen to greater renown than the master, visits frequently to discuss his romantic uncertainties. Beauchamp Blowlamp, an earnest young man who runs a dramatic Reading Society, recruits the master as a patron. Waverhouse sends elaborate letters filled with learned nonsense about Roman vomiting techniques and peacocks' tongues, all designed to tease the master about his weak stomach. The cat himself attempts to eat a leftover rice-cake, gets his teeth stuck in the glutinous mass, and ends up dancing frantically around the kitchen on his hind legs until the entire household discovers him and laughs uproariously.
The plot's central conflict begins when Madam Conk, wife of the wealthy businessman Goldfield, arrives to investigate Coldmoon as a marriage prospect for her daughter, Opula. She has an enormous hooked nose and a domineering manner, and reveals she has been spying on Sneaze's household through the rickshawman's wife and other paid informants. She demands that Coldmoon obtain a doctorate before she will consider the match. After her departure, the master and Waverhouse ridicule her appearance, and Waverhouse confesses that his claim of being a baron's nephew, which had briefly impressed her, was a complete lie.
The cat, moved by chivalry on Coldmoon's behalf, infiltrates the Goldfield mansion and discovers a household of vulgar wealth. He overhears servants mocking the master as a "terra-cotta badger" (111) and finds Miss Opula rudely arguing on the telephone and dismissing Coldmoon as having "a daft face looking like a bewildered gourd" (107). Meanwhile, Goldfield dispatches Suzuki Tōjūrō, a smooth-mannered businessman and old school friend of Sneaze, to manipulate the master into supporting the marriage. Suzuki visits and argues that the Goldfields merely want Coldmoon to earn a doctorate to establish his independence. The master begins to waver, but Waverhouse arrives and attacks the proposed match, comparing Coldmoon to a shell packed with knowledge and the Goldfield daughter to a mere promissory note. Suzuki, caught between his mission and Waverhouse's opposition, departs without resolution.
A burglar breaks into the house one night and steals clothing, the master's old blanket, and a box of yams. The cat watches from behind a trunk but cannot wake the sleeping household. The next morning, the master and his wife descend into a futile argument about compiling a list of stolen goods, during which the master coins the nonsensical insult "Otanchin Palaeologus," combining provincial slang with the name of the last Byzantine emperor, to call his wife a blockhead without her understanding. Neither the complaint nor the quarrel reaches any resolution.
The master's conflict with the neighboring Cloud Descending Hall, a private middle school, escalates as students jump the bamboo fence, launch baseballs into his property, and organize teams of provocateurs. The cat later overhears Goldfield revealing that he has been deliberately orchestrating the harassment, paying the rickshawman's wife to spy and arranging for colleagues to undermine Sneaze at his own school. A philosopher friend, Singleman Kidd, advises the master to cultivate Eastern passivity and inner detachment rather than engage in futile quarrels. However, Waverhouse later demolishes Kidd's credibility by recounting how Kidd broke his leg during an earthquake while claiming superhuman Zen reflexes and drove two disciples to mental health crises. One disciple, Pelham Flap, now resides in an asylum, and the master is horrified to learn that a letter he had read and reread with deep admiration was written by this confined patient.
The cat grows ever more philosophical in his observations. The master broods over his pockmarked face in the mirror, twirls his moustache into upturned spikes, and continues his pattern of domestic inertia. His niece Yukie, a sharp-tongued seventeen-year-old, visits and gossips about Miss Goldfield's vanity, while a student named Lancelot Yore confesses in great distress to sending a prank love letter to Miss Goldfield, terrified of expulsion. The master can offer only variations of "Well, I don't know."
The novel's threads resolve in a final gathering. Coldmoon tells a magnificently prolonged story about purchasing a violin during high school, drawing the tale out so interminably that his listeners beg him to reach the point. He then stuns everyone by announcing that he married a woman from his home province during a recent trip and no longer needs a doctorate or the Goldfield match. Shortly afterward, Tatara Sampei, the master's former houseboy now working in business, arrives to announce his engagement to Miss Goldfield and invites everyone to the wedding reception.
The conversation turns to an extended philosophical discussion about civilization and individuality. Waverhouse predicts that intensifying individualism will render marriage obsolete and art extinct, and that suicide will eventually replace natural death. Singleman argues that only Eastern traditions of mind-training can offer peace. After the guests depart, the cat, depressed by the evening's bleak conclusions, drinks leftover beer from two glasses. He grows warm and giddy, staggers outside, and stumbles into a large clay water jar in the garden. He scrabbles at the sides but cannot reach the rim; each effort to claw upward results only in sliding back beneath the surface. After exhausting himself, the cat reflects that his agony comes only from wanting to escape, and that since escape is impossible, struggling is senseless. He stops fighting, relaxes his paws, and drifts into peace. "Only by dying can this divine quiescence be attained," he reflects. "May one rest in peace! I am thankful, I am thankful. Thankful, thankful, thankful" (470).