The hero of a series of Woodhouse novels is the young Englishman Bertie Wooster, who is always accompanied by his servant Jeeves. In the novels, a kind of comedy of situations is presented, and the characters constantly fall into absurd situations, but with honor come out of them. So in the Worcester Code, Bergie finds himself in a quandary while fulfilling the assignment of her aunt Dahlia. She asks him to go to an antique shop where a silver milk jug-cow is sold of old work, and with the air of a connoisseur tell the owner of the shop that this is not an old work, but a modern one - he will begin to doubt and reduce the price. Then Uncle Tom, who collects a collection of antique silver, they say, will buy it for cheap. Arriving at the store, Bergi meets Judge Watkin Bassett, who fined him five pounds a few days ago because Bertie stole a helmet from a policeman. Sir Bassett also collects silver and is in this sense a rival to Uncle Tom, Aunt Dahlia considers him a liar. The judge recognizes Bergie and reads moral to him about how bad it is to misappropriate other people's things - while listening to him, Bergie almost dragged Bassett's umbrella, mistakenly mistaking for his own, which gave reason to friend Roderick Spode, judge Worcester of theft. However, the judge did not call the police and left the shop. Worcester begins to bicker with the owner of the shop, proving that the milkman-cow is the work of a modern Dutch master and there is no brand on it. The owner offers Worcester to go outside and in the light of day to discern the old stigma. On the threshold, Worcester steps on the cat, stumbles and with a startled cry jumps out of the shop like a bandit who has committed a robbery. The milkman-cow falls into the mud, Bergie bumps into Bassett, who is standing at the entrance, and it seems to him that Worcester robbed the shop and runs away. The name is the police, but Bertie manages to escape.

At home, he finds a telegram from his friend Gassi asking him to come to his bride’s estate and make peace with her. The bride of Gassi is the daughter of Bassett Madeleine, and Bertie is horrified by the prospect of meeting with the judge again. Then he receives an invitation from Madeleine herself. Jeeves advises Worcester to go. Then Aunt Dahlia appears and, with her request, plunges Bertie into even greater horror. She invites him to go to Bassett’s estate and steal a milkman-cow from him, because he managed to buy it under his nose from Uncle Tom, who ate too much at Bassett’s dinner and didn’t come to the store on time to buy. Bassett set up everything very cleverly, and Uncle Tom fell ill. Worcester refuses to engage in theft, but Aunt Dahlia blackmails him, claiming that he will not allow him to stand by her and enjoy the cuisine of her magnificent cook Anatole. This is unbearable for Worcester, and he goes to Bassett’s estate to reconcile his bride and groom and at the same time steal a milkman-cow.

Arriving at the estate and not meeting the owners anywhere, Bertie wanders around the house and suddenly sees a milkman-cow in the closet in the living room. He holds out his hands to him and hears a voice behind him: “Hands up!” This is Roderick Spode standing nearby, snatching a revolver, and thinks he has caught a thief. Sir VATIN appears and, with amazement, recognizes in the uninvited guest a thief from an antique shop. He is already wondering what to give him the term of imprisonment when his daughter Madeleine appears, who was in love with Worcester. They greet each other, much to Bassett's amazement. The latter claims that the abductor of police helmets, bags, umbrellas and silver cannot be a friend of his daughter. Worcester is trying to prove that he did not rob the antique shop at all, but simply tripped over the cat and rushed out too hasty onto the street. Madeleine defends him, she tells her father that Bertie just wanted to see his collection of silver, since he is a tribe nickname Traverse - Uncle Tom. Bassett freezes in place, as if struck by thunder.

Madeline then informs Bergie that he and Gassi have reconciled and the wedding will take place. Bertie meets with Gassi, who tells him that Aunt Dahlia is coming to Bassett’s estate. He tells Bertie that Roderick Spode is in love with Madeleine, but does not want to marry her, as he sees his calling in becoming the director of the fascist organization “Saviors of Britain”, better known as “Black Shorts,” . But Batkin, it turns out, is engaged to his aunt. Spode considers himself to be something like a knight guarding Madeleine, and already threatened Gassi to roll his neck if he offended her. Gassi himself is a big lover of newts and brought them with him to Bassett’s estate, they live in his bedroom - he studies how the full moon affects the love period of newts. He smells of newts from himself, and old Bassett sniffs all the time.

Gassi tells Worcester that he puts his observations and thoughts about Watkin and Spode into a notebook and that he could tell so much about Bassett that everyone would wonder how such a moral and physical freak can be tolerated. For example, when Sir Watkin cracked down on a bowl of soup - it "resembles a Scottish express passing through a tunnel." The sight of Spoud eating asparagus "radically changes the idea of ​​man as the crown of nature." During the story, Gassi discovers that the notebook is gone, he is in a panic, because he understands what the consequences will be if it falls into the wrong hands. Then he suddenly remembers that he dropped it when he got a fly from the eyes of Stephanie, Bassett's niece, and she obviously picked her up. Friends decide to find Stephanie and pick up the book from her.

Bertie catches Stephanie talking to a policeman who was bitten by her dog. Stefania makes it clear that so simply will not give the book. First, she tells about her fiancé Vicar Harold Linker - in order to win her heart completely, he must, like Worcester, take off his helmet from a policeman. Worcester, it turns out, knows him from college and tells Stiffy that Harold will definitely mix everything up. Then she says that she needs to somehow appease her uncle, who will obviously be against her marriage to the vicar - they are not rich, after all. She came up with a plan, and Harold can appear as a hero in front of Sir Watkin: Worcester must steal a milkman-cow, and Harold, in a fight, select it and give it to Bassett - then uncle will agree to marriage. Otherwise, she will not only not give the notebook to Gassi, but even threatens to throw her uncle.

Worcester meets Gassi and tells him terrible news, and he, in turn, invites Worcester to steal a book. Meanwhile, Aunt Dahlia appears with the news that Uncle Tom received a letter from Sir Watkin with a proposal to exchange the milkman-cow for Anatol's cook and Uncle Tom ponders the answer. The loss of a cook for an aunt is unbearable, and she urges Worcester to act - to steal the unfortunate milkman. He tells her that Vatkin and Spode know their intention and that Spode threatened Worcester to make a cutlet out of him if the milkman disappeared. Then Aunt Dahlia says you need to find some incriminating material on Spoud and blackmail him. This idea is supported by Jeeves and claims that such information can be obtained in a club for gentlemen’s servants called “Young Ganymede,” because a servant of such a person as Spode must be a member of the club and provide the club with all the information about his master. Since Jeeves himself is a member of the club, he will be provided with such information.

Meanwhile, Gassi escapes from Spoud, who wants to destroy him, because the engagement with Madeleine was again upset because Gassi, having met Stephanie in the living room and thinking that she was alone, tried to search her and pick up the book. Madeline saw this and interpreted everything in her own way.

Jeeves arrives and reports that Spoud can be intimidated by saying the name of Yulalia and saying that everything is known about her. What exactly, he cannot tell Worcester, since he is not a member of the club, but just mentioning the name of Yulalia will be enough to terrify Spoud. Bergie Worcester immediately has the opportunity to check all this - Spode bursts into the room in search of Gassi. Worcester boldly tells him to get out and already wants to give the name he needs, but then he discovers that he has forgotten it. Gassi flees, and Worcester entangles Spoud in a sheet. When he finally gets out and is about to break Worcester’s bones, Bertie suddenly remembers the name of Julia and calls him - Spoud is terrified and becomes submissive, like a child.

Jeeves and Worcester search Stiffy’s room for a notebook, but to no avail. Stiffy herself comes and claims that her engagement with Pinker was upset because he refused to steal the helmet from the policeman. Suddenly Pinker crawls into the window with a helmet in his hands - Stiffy is delighted, then says that Worcester is ready to help them with the abduction, as well as with the return of the milkman. Worcester refuses and demands Gassie's notebook. They argue for a long time, then Stiffy makes one condition - let Worcester go to her uncle and say that he asks for her hand; Vatkin will be horrified and call her, and she will reassure him, saying that not Worcester asks for her hands, but Vicar Pinker - this should act smoothly on his uncle. And so it happens, but Stiffy does not give the book away, but says that she hid it in the milkman, in addition, she is monitored by the local police officer Oates, whose helmet is stolen, and she secretly throws the helmet into Bertie's room.

Worcester explains to Madeline the reasons for Gassi’s act, which she misinterpreted, and asks to pick up the book, taking it out of the milkman, but it is not there. She is with Spoud, who is angry and wants to pass it to Watkin, but is forced to submit to Worcester, who takes her. But the wedding of Madeleine and Gassi is still under threat, since Gassi let the newts into the bath, and Batkin wanted to swim there. Gassi can put pressure on the future father-in-law only by taking possession of the milkman - in order to return him back, he will agree to everything. However, Vatkin, it turns out, hired police Oates to guard the milkman. You can distract a policeman only by telling him that the helmet was found in Worcester’s room - this is how Jeeves proposes to solve this problem.

While friends are thinking what to do, someone is attacking a policeman in the dark when he is trying to detain a thief who has stolen this desired item for milk and cream. The thief turns out to be Aunt Dahlia, she asks Bergi to hide the milkman in his room. But Bassett and the policeman, who had long suspected Worcester of stealing a helmet, were about to search his room. Gassi also wants to hide from Bassett in the room - he nevertheless read his notebook; Gassi begs to lower him on knitted sheets from a window to the ground. Jeeves is delighted - a way out has been found: he hands Gussey Worcester's suitcase with a milkman and helps him get down from the window.

The search in Worcester’s room yielded nothing, as Bertie threw the helmet out of the window, but, alas, the butler saw it and brought the helmet, however, the spouse appeared, took the blame and said that he had stolen the helmet with his own hand. Bassett did not initiate proceedings against him, for he was engaged to his aunt. After their departure, Jeeves confesses to Worcester that he blackmailed Spoud with the mention of Yulalia, he also offers to blackmail Watkin by initiating a criminal case for the unlawful arrest and discrediting of Worcester’s identity with witnesses in connection with the loss of the milkman and helmet. Worcester does just that, demanding instead of monetary compensation Bassett’s consent to the marriage of Madeleine and Gassi, and at the same time Stephanie and Pinker. Bassett agrees.

At the end of the novel, Worcester still asks Jeeves to talk about Yulalia - the secret is that Spode secretly makes sketches of lingerie, because he contains a store selling it, known as the “Yulalia Salon”. If his colleagues in the fascist organization find out about this, a scandal will break out, because "it is inconceivable to be a successful dictator and draw sketches of women's underwear."