The following edition of the text was used in the creation of this study guide: Newman, Catherine. Sandwich. Penguin, 2024. Kindle AZW file.

On Saturday, Rocky and her husband Nick face a plumbing issue at their Cape Cod rental. Rocky exaggerates the problem, accidentally injuring Nick with the shower curtain pole, and they later discover Nick forgot the swimsuits, which frustrates Rocky. The family, including their daughter Willa, son Jamie and his girlfriend Maya, heads out to buy new swimsuits. Rocky continues to criticize Nick for his oversight. They also visit a favorite candy store, where Maya contrasts her chaotic childhood with the seemingly simpler upbringing of Jamie and Willa.

On Sunday, Rocky and Nick argue over a breakfast pastry, leading Rocky to question if her mood might be due to menopause rather than Nick’s actions. Maya becomes ill but denies being pregnant. Rocky, Willa, and later Nick enjoy a pond swim, with Willa expressing a wish for more siblings—a sentiment Rocky shares. During a meal on the deck, Rocky reflects on the ease of having grown-up children compared to past vacations. Rocky and Nick struggle with intimacy and argue about Rocky’s feelings of carrying too much responsibility. They briefly consider splitting up but laugh off the idea. Their attempt at sex in the outdoor shower fails, and Rocky reflects on past vacations where she appeared anxious and vigilant. The family dines out and discusses the upcoming arrival of Rocky’s parents, while Rocky notices that Maya isn’t eating well.

On Tuesday, Maya confides in Rocky that she is pregnant but hasn't yet told Jamie, and she is unsure about continuing with the pregnancy. Rocky reflects on past experiences with her own pregnancies, including a traumatic doctor's visit and a past surprise pregnancy announcement to Nick. The family visits a book sale.

On Wednesday, Rocky dreams of a baby falling into the ocean and wakes up to realize she had a drunken argument with Nick the night before. Rocky’s parents, Mort and Alice, arrive at the cottage, and the family enjoys a beach outing. Mort's revelation about his grandparents' deaths in a concentration camp upsets Rocky because she never knew this before.

On Thursday, the family plans their day, and Rocky prepares complicated sandwiches to accommodate everyone’s preferences, including those of her parents.

The story then flashes back to a summer when Jamie was five, when Rocky and Nick visited a pharmacy for medication to induce a miscarriage. The pharmacist noted that Rocky had previously taken the same medication, but Rocky dismissed it as a mistake, whilst anxiously wondering whether Nick had noticed what the pharmacist said.

Returning to the present, the family enjoys a day at the beach. Willa reminds Alice to stay hydrated, and Rocky reflects on past struggles with beach outings when the children were young. During a walk, Jamie reveals he knows about Maya’s pregnancy and is upset she told Rocky first, but he intends to support Maya. Rocky feels proud of him, though she briefly panics when she thinks Mort is drowning. It turns out Mort is fine; a shark sighting had led to the water being cleared. However, Alice collapses, and an ambulance is called for her. Rocky goes with Alice to the hospital, where Alice is diagnosed with dehydration but is otherwise okay. Rocky reflects on her parents’ aging and their mortality. Willa tells Rocky she overheard Maya and Jamie discussing the pregnancy and brings up topics like accidental pregnancies and miscarriages. Rocky acknowledges having had a miscarriage after Willa was born but avoids giving details. At the hospital, Alice and Mort reveal that Alice has a heart condition requiring surgery, which Rocky is upset they had not previously shared. After Alice is discharged, the family returns to the cottage.

Later on Thursday, Rocky and Willa swim in a pond near the cottage. While swimming, they scream in panic, thinking they’ve seen a snake. After calming down, they continue discussing pregnancy. Willa criticizes Rocky for not telling Nick about Maya’s pregnancy and presses her on the topic of miscarriages. Rocky explains that she had an abortion because she felt overwhelmed by the idea of another baby so soon after Willa, followed by a miscarriage the next year. Nick overhears the conversation and Rocky panics, revealing to Willa that Nick did not know about the abortion. This leads to an emotional confrontation between Rocky and Nick, culminating in a heartfelt reconciliation.

On Friday, Rocky and Nick start their day by having have a heartfelt conversation where Rocky reveals her struggles with past abortions and miscarriages, and Nick expresses his hurt over being kept in the dark. As they drive back to the cottage, Rocky finally informs Nick about Maya’s pregnancy, leading to a tense exchange where they both express their frustrations but ultimately reconcile. Alice and Mort prepare to leave despite Alice’s health issues, and Nick offers to drive them, but they decline. Jamie and Maya announce their engagement but don’t mention the pregnancy, and Rocky suggests a wedding in their yard, though Maya prefers her parents’ house.

After Alice and Mort leave, Rocky and Willa discuss Rocky’s abortion, with Rocky expressing regret, which conflicts with her political beliefs. They encounter a mother and daughter, which prompts further reflections on parenting. The family decides to buy sandwiches instead of Rocky making them for everyone. They spend their last day at the beach. Rocky and Nick argue about his lack of emotional openness but later share ice cream, and Rocky contemplates how trying to preempt loss doesn’t prevent it.

The final chapter of the novel details the aftermath of Alice’s death from heart failure. Rocky reflects on her final moments with her mother and the family’s gathering to scatter Alice’s ashes. At Jamie and Maya’s wedding, Willa’s toast advises against keeping secrets in relationships.