Rules for the Summer

The novel opens with Theodore "Theo" Williams, a wealthy British man and heir to the Lord Dunebary title, kneeling on Renley Gossage's front lawn in Cape Meril, Massachusetts, to propose marriage. He gets her name wrong multiple times, requiring whispered corrections from his best friend, Rupert. Renley flatly refuses, bewildered that a stranger she matched with online has appeared with a ring. Theo flops onto her grass and announces he has rented the house next door for the summer, vowing to win her over.

A flashback reveals how Theo arrived. One drunken night, Rupert dares Theo to create a profile on Fiance-er.com, a website for people seeking marriage partners. The next morning, Theo's domineering father, Lord Dunebary, who has groomed Theo since birth to inherit the family title, discovers a tabloid article about the profile and berates his son. Rather than admitting it was a joke, Theo doubles down, claiming he is genuinely seeking a wife. Lord Dunebary issues an ultimatum: Theo must be engaged by summer's end, or his father will arrange a marriage with his family friend Neil's daughter, a woman Theo finds deeply unappealing.

Meanwhile, Renley, a handywoman known as a "Jackie of all trades," wins a bid from Cape Meril's business society to take over Rudder's Sweets, a beloved candy shop connected to her late father. She discovers that her Aunt Kitty, her only remaining family and housemate, does not have the $20,000 they need for renovations. Marjorie, who works for both the bank and the mayor, reveals that the business society awarded Renley the bid expecting her to fail so they could sell the storefront to a national chain.

That night, drunk on Aunt Kitty's homemade margaritas, Renley and her aunt search online for a financial backer. Aunt Kitty's cracked tablet causes them to confuse Fiance-er.com with a financier website. They find Theo's profile and interpret his dating preferences as business terms, reading "DTF" as "down to finance." They match with Theo and send their address, believing they have secured a wealthy British investor.

When Theo and Rupert arrive expecting a willing fiancée, the misunderstanding becomes immediately apparent. Renley's friend and neighbor Tilly, a local artist, discovers the mix-up and explains that Renley matched with a fiancé, not a financier. Renley orders them to leave, but Theo persists, following her around town and offering money for the shop. She is skeptical until Aunt Kitty drags her to Theo's house, where he proves he can transfer $30,000 immediately.

They strike a deal: Theo gives Renley the money in exchange for daily morning walks where she must talk to him. Renley drafts formal rules: no buying affection, no flirting, no proposing, and a requirement that she teach Theo practical skills. Theo adds that Renley cannot date anyone else and that he reserves the right to keep pursuing her.

Through their walks, renovation work, and escalating banter, a genuine connection develops. Theo helps at the shop with infectious enthusiasm despite comically struggling with basic tools. One evening, Rupert and Aunt Kitty secretly arrange a romantic setup with chocolate-covered strawberries and wine. Afterward, Renley and Theo lie on the grass outside their houses, holding hands and both independently choosing the name "Horace" for a shooting star.

Their first kiss occurs on the beach after a dinner where both open up about their families. Theo shares that his father was physically and verbally abusive. Renley reveals that her father lied about important jobs while secretly beachcombing for items to pawn, and that her mother left the family when Renley was young. Ira, the candy shop's previous owner, was one of the only people kind to the Gossages, which is why the store matters so deeply. On the beach, Theo tells Renley he believes in her, and they kiss.

Renley pulls away afterward, reestablishing distance. Theo leaves for a short trip to Boston with Rupert, confiding in their Uber driver, Lamar, about his growing feelings. When Theo returns early, Renley pulls him in for a kiss without hesitation. She drafts new rules declaring they "should just be friends." Theo accepts most rules in writing but rejects the friendship provision. Their intimacy intensifies nonetheless through nightly swims at a secret pond, where rounds of truth or dare eventually lead to sex. Afterward, floating in the water, Renley whispers, "Please don't hurt me."

Tension builds on multiple fronts. Aunt Kitty repeatedly fails to help, devoting her time to hobby horse training with Rupert. Renley breaks down after another broken promise, and during a drive she admits that her aunt's unreliability mirrors her father's and leaves her feeling exhausted and alone. Theo tells her he is still deciding his future regarding the title, signaling he may not return to England. He formally asks Renley to be his girlfriend, getting on one knee with the revised rules, and she says yes, insisting they keep the relationship secret from Aunt Kitty. Theo's friendship with Rupert also fractures: Rupert, rejected for a volunteer teaching position abroad and feeling neglected, leaves for a bed-and-breakfast.

Recognizing that secrets will damage the relationship, Theo confesses everything to Renley: the dare, his father's ultimatum, and his initial intention to convince her to marry him. He tells her his feelings became real. Renley is hurt, telling him his confession makes her feel like "a tool," but she does not walk away. The next morning, Theo's mother calls: His father has had a heart attack, and Theo must return to England immediately.

At his parents' estate, Theo discovers his father scheming from his hospital bed. Lord Dunebary announces that both Theo and his sister, Elizabeth, must marry partners he has chosen. For Elizabeth, who is in a committed relationship with a woman named Hannah, the chosen partner is a male ex-boyfriend. Their father threatens to make Elizabeth's life miserable if Theo refuses. Elizabeth forces a reconciliation between Theo and Rupert; Rupert apologizes and books Theo a flight back to the States. Emboldened, Theo confronts his father, refusing the title, the arranged marriage, and the entire life designed for him. His father threatens to disown him, and Theo accepts.

Back in Cape Meril, Marjorie informs Renley that the business society has given her only five days to open the shop or lose it. Emotionally drained, Renley gives up. When Theo arrives, he takes immediate action: He and Rupert drive to a wholesale candy store in Boston with Lamar, purchasing enough product to stock the shop. Lamar arranges a feature on a local morning news show, and Tilly secures the inspection permit.

Tilly brings Renley to the shop under a pretense. Inside, Theo surprises her with shelves fully stocked, windows painted with the Rudder's logo, and a team ready to help. Aunt Kitty arrives wearing an apron from a local market, revealing she has gotten a real job. She apologizes for years of broken promises and for letting Renley become the parent in their relationship. They reconcile and prepare for the opening together.

In the epilogue, Rudder's Sweets opens to enormous success. That evening, Renley and Theo celebrate at the pond. Renley tells Theo she loves him, explaining she waited to say it in a moment separate from the shop so he would know her love is for him, not for what he did. They play one final round of truth or dare: Renley chooses dare, and Theo says, "I dare you to marry me." Renley accepts, and Theo announces to the fireflies and stars that she said yes.