Grace Porter has spent seven years as the personal assistant to Gabriel Ferrara, the demanding CEO of Ferrara Media in New York. Each morning, she enters his office to review his schedule while he dresses, captivated by the man she secretly loves. Gabriel is brash and critical, calling Grace "Miss Porter" in public and "Gracie" in private, and ordering her to send flowers and gifts to the women he dates. Grace is 29, hopelessly in love, and has refused to date anyone else. When Gabriel asks her to book a hotel for a romantic weekend with a new woman, she resolves to leave. Inspired by a stranger in the park who urges her to stop waiting for life to begin, Grace searches for properties in Greenville, Maine, a town she fell in love with at her cousin Debbie's wedding years earlier.
Six months later, Grace hands Gabriel her resignation. She has bought a house in Greenville and trained a male colleague to replace her, deliberately choosing a man so no other woman will watch Gabriel dress. She has already emailed HR, and her last day will be December 22nd. Gabriel tears up the letter, fabricates a gas leak to clear the office floor, and offers escalating pay raises, all of which Grace declines. She tells him she wants a home, a garden, a dog, and maybe a family. Gabriel falls silent, signs her leave documents, and dismisses her coldly. Grace returns the next morning, determined to work her final days and attend the Christmas party. At the party, she wears a red dress, but Gabriel leaves without saying goodbye.
Grace enters Gabriel's darkened office for a final look and finds him in the corner with a drink. He pushes her onto his desk and they have sex, intense and desperate. He reveals he has wanted this for years. Afterward, he becomes cold, acting as if nothing happened. Grace storms out, but Gabriel's driver, Mark, redirects her car to Gabriel's penthouse. There, Grace is overwhelmed and tries to leave, telling him she is not a casual person. Gabriel softens, apologizes, and asks for one night to say goodbye. He carries her to the shower, where they make love tenderly throughout the night.
The next morning, Gabriel is dressed and working. When Grace suggests staying in New York and finding another job so they could be together, he tells her his heritage demands he marry an Italian woman and that his children's first language must be Italian. He calls their night "a gift that we gave to ourselves" and drives her home. Grace opens the Christmas present he labeled as a pen and discovers a diamond tennis bracelet, recalling his earlier statement that he would only buy a diamond for someone he loves. The card reads: "To my Bracie, Forever yours, Gabriel."
Grace moves to Greenville and, six weeks later, discovers she is pregnant despite being on the pill, likely due to antibiotics. Debbie accompanies her to the doctor, where Grace learns she is carrying fraternal twins. She travels to New York to tell Gabriel, but he ignores her call. The next day, the receptionist at Ferrara Media says he is booked all day. Grace leaves humiliated, changes her phone number, and flies home. Sections from Gabriel's perspective reveal he was in a board meeting when she came, and when he discovers her phone is disconnected, he asks Mark to find her. Mark challenges him, asking what he plans to offer a woman he refuses to marry. Gabriel reluctantly lets her go.
Grace gives birth to the twins via C-section: a boy named Dominic and a girl named Lucia. She tells everyone the children were conceived through donor sperm, keeping Gabriel's identity secret. She hires a young Italian nanny, Maria, to teach the children Italian from infancy. Grace works at a bank and begins a two-year relationship with a warm mechanic named Russel, but when Debbie warns her that Russel plans to propose, Grace realizes something fundamental is missing and they break up. Meanwhile, Gabriel dates an Italian woman named Ariana Rossi for over a year. Ariana proposes and he accepts, though he privately admits he never would have proposed himself.
Seven years after Grace left, Gabriel encounters a former employee who mentions that Grace was heavily pregnant within the year she departed. He calculates the timeline and arrives at her home unannounced. Lucia comes outside, and her dark Italian features confirm his suspicions. Dominic pushes Gabriel away, shouting at him to leave his mother alone. Gabriel sends a doctor for paternity tests, which Grace initially refuses. He confronts her at her workplace, and she admits he is the biological father. Grace delivers a firm ultimatum: He must be a fully committed, present father or stay away entirely.
Gabriel visits for what he intends to be a final goodbye. At dinner, the children speak Italian and he is overcome with emotion. Grace reveals she hired an Italian nanny to prepare them for his world. He says goodbye at Dominic's Little League game, hugs each child, and walks away. The decision does not hold. Gabriel confides in his close friend Claire that he is still in love with Grace and breaks off his engagement to Ariana. Gabriel's mother, Elena Ferrara, then travels to Grace's workplace uninvited and offers her 20 million dollars to disappear, calling the twins "bastard illegitimate children." Grace refuses and has Elena escorted out. Gabriel rents a property in Greenville, moves there part-time, and tells the children he is their father. Lucia is thrilled. Dominic coldly states he does not want a father.
Grace and Gabriel's physical tension breaks, and they have sex again. The next morning, Ariana arrives at Grace's front door, hysterical, and Gabriel flies her back to New York. Grace and Gabriel enter a tentative relationship marked by vulnerability and conflict. He finds a box of notes and poems Grace kept during her pregnancy, confirming her feelings were never one-sided. Grace falls down a flight of stairs at a school dance, suffering a broken wrist, torn ankle ligaments, and a concussion requiring an induced coma. Gabriel stays at her bedside and, when her parents arrive, tells them he and Grace had dated for over a year, shielding her from shame. During her recovery, Gabriel reveals the root of his resistance: His own father, also a Ferrara CEO, had an affair with his PA, left the family, and devastated Gabriel's mother. Gabriel had been terrified of repeating that pattern. Grace tells him she loves him and has always loved him but that he broke something inside her. He proposes they try a relationship without sex to rebuild trust.
Grace decides to move the family to New York during the week, returning to Greenville on weekends. Gabriel takes her to the lake house for an elaborate first date, presenting a handmade book titled "You Hung the Moon," compiled from her secret notes interspersed with his own declarations. He proposes, and she accepts. They marry in Sardinia with only the twins, Mark, and a photographer present, fulfilling Grace's long-held dream of visiting the island. A year later, Grace is pregnant with their third child. Ariana attempts to disrupt their life at a restaurant by claiming she is pregnant with Gabriel's child, but Gabriel dismantles the lie with evidence. When Grace goes into sudden labor at home, Gabriel panics and delivers the baby in the car. The baby is a girl. Gabriel names her Luna Grace, explaining: "Because her mother hung the moon."