In the present, 60-year-old Lucy wakes after a major “spell.” Sarah has canceled their planned trip to Italy. Lucy retreats to his study, feeling shame over his betrayals of Sarah, and resolves to stop writing his memoir. He has reached a good stopping point: the moment at which Sarah has enters his life and draws him and Bobby together again.

The narrative flashes back to Lucy and Sarah’s first years of college. Sarah attends Cooper Union in New York City while Lucy goes to Albany State. Sarah writes letters full of self-doubt about her artistic talent. Lucy lies about his college experience, claiming to be adjusting well when in reality he is lonely and returns to Ikey’s every weekend. He resents Sarah’s courage and worries that she still has feelings for Bobby. During Christmas break, Lou’s fears prove unfounded, as Sarah is happy to be home with his family, though she notes that everything in Thomaston looks smaller after her time in Manhattan.

In January, Big Lou is diagnosed with cancer. Lucy changes his college schedule to work at Ikey’s four days a week, angering Tessa, who wants him focused on school. Their conflict intensifies. In March, Uncle Dec announces a month-long California vacation. Tessa begins renovating Dec’s apartment, and Lucy wonders how she can afford the work. Lucy becomes paranoid that Tessa is warning Sarah away from him and Ikey’s while his father encourages her to stay.

On the last evening of spring break, at a fancy restaurant, a despondent Lucy accuses his mother of wanting his father to die so she can sell the store. He nearly voices his suspicion that Tessa and Dec were the couple on the trestle on the night he was locked in a trunk by bullies as a child. As a “spell” begins, Sarah takes his hand and explains the truth: Tessa would rather sell their house than Ikey’s; she is renovating the apartment for Sarah and Lucy to live in after they marry. The “spell” dissipates. Relieved, they plan their future together.

Back in the present, Lucy reflects on his depression after his father’s death, during which he created a map of cruelty by putting black pins on a map of Thomaston to mark deaths and other tragedies. Sarah joins him and reports that his mother thinks he should get another neurological exam. She reveals his mother’s theory that he is still psychologically trapped by the childhood incident where he was locked in a trunk. Lucy confesses that during his “spell,” he entered Sarah’s painting and saw his father on the Bridge of Sighs. He then reveals that he intercepted her letter to Bobby, reciting it verbatim, and admits he was afraid she would fall in love with Bobby again.

In present-day Venice, 60-year-old Robert Noonan meets his art dealer, Hugh, on a hotel terrace. Robert has started a new painting, Sarah at the Window, which came to him in a dream. He reveals that the dark self-portrait is actually of his father. He reflects on the occasional dreams that have guided his work throughout his life.

In flashback to age 17, Robert recalls his first and most vivid paint dream of a vast, beautiful cathedral. It occurs on the morning of his final high school football game, after he has moved into a squalid flat above the Rexall drugstore. During the game, his senses feel heightened, and he observes Sarah’s father, Mr. Berg, buying drugs from a man named Jackson.

After the team’s victory, Coach Halliday gives a speech on teamwork, which Perry Kozlowski echoes emotionally, declaring his teammates brothers forever. In the parking lot, Robert’s father waits for him, reveals that he has attended all of Robert’s games, and invites him for a beer at Nell’s. There, Robert meets Maxine, the bartender, and her son, Willie, who has Down syndrome. His father reveals that he arranged Robert’s job at Murdick’s and that he owns Nell’s. They argue about Robert’s mother until Willie, sensitive to conflict, emerges distressed from the kitchen, forcing them to calm down.

When his father returns from the restroom, he looks a decade older, making Robert realize he hasn’t been paying attention. Outside, his father reveals that Maxine is the woman he has been having an affair with for years. As Robert leaves, he finds his father’s leftover prime rib in his saddlebag and eats it ravenously.

At Ikey’s, he finds his friends in their usual configuration. He, Lucy, and Sarah wait at Ikey’s for his girlfriend, Nan Beverly, to pick them up. Dec Lynch arrives and starts a tense argument with Big Lou about not taking Tessa out, making an ominous comment before storming off. Robert gives Sarah a ride home on his motorcycle. While sitting in her driveway, she cries, fearing they will all end up like their parents. She reveals her father hates Lucy and wants her to date Robert instead. Robert asks if she thinks something is going on between Dec and Tessa; Sarah firmly denies it. After she goes inside, Robert watches her in her lighted window and knows with certainty he is in love with her. He returns to Nell’s, where his father asks what he wants and offers to help with college expenses. Robert asks his father for advice about the two girls in his life.

In present-day Venice, Robert Noonan takes fellow artist Anne Brettany to dinner. The next morning, he reflects on his two paintings of his father and Sarah, recognizing how they parallel the intertwined lives of his friends and their parents during his senior year of high school.

In flashback, Robert remains suspicious of Tessa Lynch, though things at Ikey’s return to normal. He establishes a truce with his father, their relationship now centered at Nell’s, where Willie’s sensitivity to anger prevents conflict. Robert begins bartending at Nell’s alongside Maxine. His brother, David, reveals that he saw their mother kissing the phone company man. Meanwhile, Sarah’s stepfather has alcohol dependency, and her mother has resumed drinking heavily.

Mr. Berg’s behavior grows increasingly erratic after his ex-wife’s remarriage. He gives a bizarre, impassioned performance as Captain Ahab in honors English class, which Lucy confronts him about. Mr. Berg finishes his novel and submits it to publishers but receives a series of form rejections. Robert is not in love with Nan Beverly. Sarah advises him not to lead Nan on, as she is vulnerable. Nan is increasingly anxious about sex and her social standing.

In late March, a major blizzard begins. Nan’s parents have separated, and her mother has flown in from Atlanta for a bitter confrontation. Nan appears at Ikey’s, distraught. The friends leave together. On the dark landing of his building, he kisses Sarah. She calls it just a kiss, then sends him off to take care of Nan. Robert takes Nan to the Cayoga Diner, then on a tour of the West End, where they encounter a drunk Dec Lynch. Nan decides she wants to have sex with Robert. They go to his squalid flat, where the sight of Sarah’s easel unnerves Nan, but they have sex anyway.

Before dawn, Nan wakes panicking, gets violently ill, and demands to go home, inadvertently splitting Robert’s lip. Outside, Robert’s father is waiting; Mr. Beverly has threatened to call the police. As Robert drives Nan home, they pass Big Lou, who looks hurt. At the Beverly house, Mr. Beverly tries to punch Robert, slips on ice, and gets stuck under the car with a dislocated shoulder. Mrs. Beverly screams at Robert, calling him a monster, and orders him to leave without his father’s car.

Robert walks to Ikey’s and spends all day helping the Lynches shovel snow, feeling a powerful sense of pride and belonging. Lucy tells him Nan called and lied, claiming nothing happened between them. That evening at Ikey’s, Sarah learns that her mother and stepfather were killed in a car accident during the blizzard. Her father burned his novel manuscript upon hearing the news. Robert sees Sarah turn to Lucy for comfort and knows he has lost her.

That night at his flat, unable to sleep, Robert reflects on his cathedral dream and realizes it represented home, though he now understands he belongs nowhere. He senses the dark events of the coming months gathering force: Nan’s departure for Atlanta, Mr. Berg’s arrest for drug possession, and his own final, violent confrontation with his father after learning his mother is pregnant again. He concludes that Sarah was wise to choose Lucy.