Jim Qwilleran, news reporter for The Daily Fluxion and former crime reporter, is assigned to review restaurants. For his first story, he decides to review Maus Haus, owned by Robert Maus. In addition to a restaurant, the architecturally peculiar historic building is also a boarding house. When Qwill discovers there is an open apartment, he promptly moves in with his two Siamese cats, Koko and Yum Yum.
Also in residence at Maus Haus is Joy Wheatley, Qwill's old girlfriend from Chicago. She had found out she had a knack for pottery, and married a potter named Dan Graham. It soon becomes obvious that the relationship between Joy and Dan is strained, especially when they discuss how Joy’s cat went missing one day. Joy is deeply troubled by this, but Dan jokes about it. Joy is a far more successful potter than Dan; he is missing one thumb and so can only make roll pots, not as appealing as those spun on a wheel. One night she privately tells Qwill that she would divorce Dan if she could afford the court case. Qwilleran decides to lend her $750, the last of the prize money he won for a series of news articles.
Later that same night Qwilleran hears a scream, and then a car pull out of the garage and drive away. The next day, Dan claimed that Joy has left him. He also brushes the scream off, as he claims Joy was working on an electric wheel and got her hair caught in a pot. She was saved by Dan when he threw the switch, shutting the wheel off and preventing her from being scalped.
A few days later, one of the other residents of Maus Haus mentions how well Joy threw pots on her manual, not electric, wheel. Qwilleran begins to suspect Joy is dead. Shortly thereafter another mystery comes to Qwill's attention: Max Sorrel, a resident of Maus House, owns a restaurant called the Golden Lamb Chop which is suffering a spate of anonymous rumors about how the meat is cat, the chef has a terrible disease and other equally damaging tales. This has scared off the customers, leaving the restaurant near bankruptcy. Qwilleran decides to review the Golden Lamp Chop, but before he writes it, he gets a threatening phone call advising him not to write anything about the Golden Lamb Chop. He does so anyway.
Dan gets a passport, claiming he will be going to Europe to display his pots. Qwilleran also learns that the car that drove off after the scream in the night was Max Sorrel’s speeding off after learning his restaurant was on fire. The houseboy says Joy always used the kick wheel, and that “Mr. Graham was going to blow a whole load of pots” because he was heating the kiln too quickly. The houseboy spied on Graham by using a peephole cut in the wall of Qwill’s room.
The next morning, the houseboy is nowhere to be found. Dan claims he received a postcard from Joy in Florida, who asks to have her summer clothes. Hixie Rice, a resident of Maus House, breaks off her engagement with Graham as she does not want to be with a man cheating on his wife.
When Qwill peers through the same peephole the houseboy had used, he sees Dan copying things out of a ledger. To get a better look, Qwilleran claims Fluxion wants a photo shoot of Dan's pottery, and brings Koko along to pose in some pictures (though he really wants the cat to sniff around for clues). Koko does show great interest in the trap door to the basement, but Dan says that they shouldn’t go down there because there are rats. But Qwill later learns that Maus is very particular about sanitation, and has an exterminator in regularly. Also, Qwilleran finds the ledger Dan was copying out of, and discovers it was a recipe of glazes used by Joy.
Koko types "pb" on Qwill's typewriter— the chemical symbol for lead. Qwilleran looks through the peephole, and witnesses Dan burning Joy’s clothing.
At the pottery opening, Dan surprises everyone with his“living glaze,” which compensates for the poor quality of his pots. Many people said that if his glaze was put on Joy’s pots, than they would be very popular. Qwilleran asks a diver friend to look below the boardwalk behind Maus House, after the housekeeper tells him she saw someone dumping abag into the river. The diver reports the bag contains Joy’s pots with the living glaze. That night, Qwilleran reads a book on pottery, which provides the missing clue:
That evening, Dan breaks into Qwill’s apartment to kill him, but Koko and Yum-Yum had spun a spider web of yarn from a yarn ball throughout the apartment, causing Dan to trip and fall. Qwilleran is alerted, and Dan is arrested. As for the Golden Lamb Chop slander, Charlotte Roop overhears two Heavenly Hash House managers discussinghow their attempts to put the restaurant out of business had failed. They had wanted to buy the property where the Golden Lamb Chop was located.