Set in Paris at a sex club called Legacy, formerly known as L'Amour, the novel follows 25-year-old Amelia Kade, a designer and co-owner of the club, and 53-year-old Matis Moreau, her godfather and her father's lifelong best friend. Amelia has harbored a secret crush on Matis since her teenage years, while Matis, a retired club owner and lifelong bachelor, has only ever seen her as his goddaughter.
The novel opens with a prologue set two years earlier, in which Amelia's father, Ronan Kade, emails the six younger co-owners to announce his retirement and pass the club to them collectively. Amelia is disappointed that Matis is also stepping down. The group agrees to take over, renames the club Legacy, and toasts their new venture. Amelia privately resolves to get over her feelings, dismissing the idea of Matis ever returning them as delusional.
Nearly two years later, Amelia works in a studio at the club, sketching designs for a designer incubator program. She has attention-deficit/hyperactivity disorder (ADHD), struggles with self-doubt, and cannot commit to projects or relationships because of her fixation on Matis. When Matis visits her studio, he treats her with affectionate detachment, calling her by his longstanding nickname, Trouble. He casually mentions he is meeting a woman at the club that evening, devastating Amelia.
From Matis's perspective, sex has grown hollow. He reflects on retirement with melancholy, feeling purposeless. Visits to his mother, Estelle, who has advanced dementia and no longer recognizes him, deepen his sense of isolation. He envies Amelia's creative energy but categorizes her as off-limits.
At a weekly family dinner at the restaurant owned by Amelia's best friend, Freya, Matis admits he is lonely and has never seriously dated. Amelia offers to help him set up a dating profile, and Matis proposes a trade: She helps him with technology, and he helps her find a worthy boyfriend. Amelia confides in Freya afterward that her real plan is to force herself to move on by helping Matis find someone else.
On the Métro, Amelia builds Matis's profile while he rejects every potential match for her, declaring no one will ever be good enough. He receives his first match, a woman named Laura, and resolves to pursue her, though their growing closeness feels like something beyond a godfather-goddaughter bond.
Matis takes Laura to the club after their first date. They end up in the voyeur room, a space with a viewing couch separated from a bed by a sheer curtain. Amelia, who had reserved the room to sketch, fell asleep and overslept her reservation. She wakes to find Matis and Laura entering and watches from behind the couch. Instead of jealousy, she discovers she is profoundly aroused by the act of watching, which quiets her racing mind. Matis accidentally moans Amelia's name, and Laura storms out. A broken pencil reveals Amelia's presence, and a horrified Matis insists the slip meant nothing before pulling her into a wordless hug and leaving.
Matis avoids everyone for four days. When Amelia confronts him at his apartment, they talk openly, and he validates her voyeuristic discovery as a normal kink. Amelia mentions that a young American tourist named Jacob asked for her number, and Matis stiffens with jealousy.
Their resistance erodes through escalating encounters. When Jacob invites Amelia on a double date with his sister Olivia, fellow co-owner Weston Scott suggests Amelia bring Matis, theorizing it may provoke him into revealing his feelings. On the dance floor, Amelia locks eyes with Matis just as Jacob leans in for a kiss, and she is overwhelmed by sensory overload. Matis rushes to shield her, calming her with his touch. Afterward, they take the long way home through nighttime Paris. At Trocadero, the plaza beneath the Eiffel Tower, he asks her to dance and hums
La Vie en Rose in her ear. When Amelia asks him to kiss her, he does, but the kiss escalates until he pulls away in panic.
Later, Matis discovers his own red plaid scarf hanging behind Amelia's bedroom door. Recalling her brother Julian's story about Amelia stealing her crush's scarf in high school, he realizes she has been in love with him for years.
Despite repeated attempts to stay away, Matis cannot resist. He invites Jacob and Olivia to the club without telling Amelia, trying to push her toward a more appropriate partner. In a furious office confrontation, he admits he aches for her, and Amelia pulls him into a fierce kiss. Their physical relationship begins that night, with Matis setting a boundary of everything but penetrative sex. Amelia suggests Matis could be with others while she watches, accommodating both his fear of monogamy and her voyeurism.
Their secret quickly leaks. Julian discovers them and is furious but relents after Matis confesses he loves Amelia. Geo, the bartender and Matis's old friend, promises discretion. Phoenix, a fellow Legacy co-owner, nearly catches them at a birthday dinner but proves supportive rather than judgmental.
Ronan has purchased a club in London and offers Matis the job of running it. One night, Matis climbs the drainpipe to Amelia's balcony, and they have sex for the first time. As their relationship deepens, they have unprotected sex at Matis's apartment. The next morning, Amelia answers a knock at his door without checking. Ronan stands in the hallway. Seeing his daughter in yesterday's dress and his best friend shirtless, he is devastated and accuses Matis of betrayal.
Matis confronts Ronan, who tells him to take the London job and leave Amelia alone. Matis refuses. When Amelia faces her parents, she draws a parallel to their own unconventional love story: Ronan once dated her maternal grandmother, and there is a 35-year age gap between her parents. Her mother, Daisy, believes Matis truly loves Amelia and advises her not to lose herself in a relationship. Amelia packs to move out, and Matis arrives to leave with her.
Matis travels to London to tour the club, but the separation is agonizing. Watching a young father with a small child on the street, he realizes his future is with Amelia, not in London. He declines the job and returns to Paris.
Amelia's fashion show at Legacy, her project for the incubator program, is a success. Backstage, Ronan watches Matis calm Amelia's anxiety with quiet reassurance. Afterward, Ronan acknowledges for the first time that Matis truly loves his daughter and tells him the best years of his life are still ahead.
After the celebration, Matis texts Amelia a selfie with the Eiffel Tower behind him. She races to Trocadero and finds him alone on the plaza. He kneels and proposes with a gold band set with a red ruby. She says yes.
In an epilogue set seven years later, Amelia comes home to their Paris apartment, pregnant with their third daughter. Five-year-old Stella is applying makeup to Matis's face while three-year-old Maisie giggles beside them. Amelia runs a children's fashion brand called Stella Moon, with profits funding Alzheimer's research in honor of Estelle, who lived with the family until her death.
La Vie en Rose plays on the speaker, and Matis pulls Amelia up to dance around the kitchen, as he has done every time the song has played in their nearly seven years of marriage.