The following version of this book was used to create the guide: Hazell, Lottie. Piglet. Henry Holt and Company, 2024.

Lottie Hazell's novel Piglet is set in Oxford, England and told from the third-person point of view. Tracing the days leading up the protagonist Piglet's wedding, the novel is written in the past tense and toys with conventional notions of the linear narrative plot line. For the sake of clarity, the following guide relies on the present tense and a more streamlined mode of explanation.

Shortly after Piglet and her fiancé Kit move into their new house in Oxford, they invite their friends over for a housewarming party. Piglet goes to her favorite supermarket, Waitrose to shop for the dinner. Determined to awe her guests and prove that her life with Kit is as great as she has said it is, she chooses elaborate recipes and ingredients. On the night of the dinner, everything goes well. Kit's friends Seb and Sophie and Piglet's friends Margot and Sasha commend Piglet's efforts and compliment her food. However, after dinner is over and everyone starts drinking and chatting more leisurely, Piglet feels tired and overwhelmed. She and Margot dismiss themselves to the garden so Piglet can smoke. The old friends talk about Piglet's upcoming wedding, and Margot's due date.

Piglet spends the following weeks going to work at Fork House, a cookbook publishing house, and preparing for her wedding. She visits the gym with Kit's mother Cecelia and hosts her parents, sister, and her boyfriend for dinner. When Linda and John, Franny, and Darren arrive, Piglet is anxious about making the night perfect. Things go well until Linda and John start sharing stories from Piglet's childhood. They ridicule her for always eating too much, a habit that won her "Piglet" as a nickname. They recall the time she ate Franny's entire birthday cake. Piglet says nothing, but she remembers the incident differently. She ate the cake because Franny had developed an eating disorder and did not want to eat around other people. To protect Franny, Piglet had gotten into the habit of eating her sister's portions for her.

After her family dinner, Piglet tries to let go of her upset. She reminds herself that she has a good life with Kit. She tells him how happy she is to have found him.

Thirteen days before the wedding, Kit reveals a dark secret about himself to Piglet while they are lying in bed one night. Shocked, Piglet does not know what to say.

Over the following days, Piglet tries to decide what to do. She has built her entire life around Kit and fears that getting mad at him will ruin their future plans.

Seven days before the wedding, Piglet, Margot, Linda, and Franny go to the bridal shop for Piglet's fitting. The dress does not fit. So, she decides to fast before the wedding. Then Margot's water breaks. Piglet races her back to the house where they will meet Sasha. To distract Margot from her pain, Piglet tells her Kit's secret.

In the days after Margot gives birth, she repeatedly tries to contact Piglet. She is worried about her and does not want her to marry Kit given his past. Feeling betrayed, Piglet ignores Margot.

On the day of the wedding, Piglet's entire family has to help her into her wedding dress. Furious at Piglet for her lack of self-control, John berates her for being greedy. At the church, Piglet feels on the verge of tears, but she goes through with the ceremony. Immediately afterwards, she realizes she has made a mistake.

At the reception hall, Kit confronts Piglet for her distant behavior. Piglet reveals that she cannot be married to him after all. She tears herself away, races into the kitchen, and eats alone. During the reception, Piglet continues eating with abandon. Finally, she grabs the microphone and exposes Kit's secret to her guests. She races out of the hall, borrows Darren's car, and drives to Margot's. Over tea, Piglet tells Margot everything that happened. The next morning, the friends catch up before Piglet returns home. On her way, she buys groceries to make herself a nice pasta dinner. Back at the house, she meets up with Kit and tells him they cannot stay married. After he leaves, she makes her pasta and eats only what she wants.