In 1971, civil servant William Coughlan, seeing a sunbeam on his desk blotter, suddenly feels inspired and quits to become a painter. This shocks his wife Bette Coughlan and their 17-year-old son Nicholas Coughlan.
Simultaneously, on a west coast island, Isabel Gore and Sean Gore watch the sea as he inexplicably collapses, becomes withdrawn, and is confined to a wheelchair. Soon after, Isabel is sent to be educated by the mainland under the care of the Mother Superior as island custom dictates, while her parents Margaret Gore and Muiris Gore decide it is time.
Back in Dublin, as the painter William searches for inspiration, he heads to the western coast. Three months pass and mother and son suffer, wondering if he will return.
Meanwhile, Isabel escapes from the school. When Peader O Luing Peader O Luing happens to be driving by, he helps her over the fence. After returning to the school, Isabel is told to kneel in contrition, but she tires of the ritual.
When William returns to Dublin, Nicholas is relieved, hoping life will resume. But at home, William visits Bette in the bedroom, finding her dead. He then insists on returning West for another week, upsetting Nicholas.
Poet and schoolteacher Muiris Gore laments Sean's prolonged incapacitation, unable to write. At the school, Peader convinces the nuns to release Isabel, supposedly for a funeral. They head to a pub, dance, and kiss.
Nicholas secretly follows William on the bus west, briefly crossing Isabel's path as she spends the day with her parents. He accompanies him to the sea; when Nicholas fears William may drown, he follows him in. William saves Nicholas and muses that God still wants them around.
Isabel returns home, claiming the school gave her time off, and Margaret grows suspicious. The young woman wheels out to tell Sean about Peader. Muiris is glad to see her and tries to calm Margaret.
The Coughlans stay a while so William can paint. Before returning to London, all but the painting Nicholas carried is spoiled. Back in Dublin, William donates the piece to a poetry competition.
Isabel's lie to the nuns is discovered and she is turned out. She seeks Peader in his family's shop; discovering he has pined for her, he greets her warmly. Meanwhile, back in Dublin, William dies in a house fire while Nicholas completes his degree.
Three months pass. Margaret visits Isabel, who now regards Peader with less enthusiasm and wonders if she is pregnant. Peader's mother cautions that he seldom stays in love for long. Isabel confronts Peader; he admits his pattern but asks her to marry him.
On her wedding day, Isabel confides in Sean that she is unsure about Peader. Along the coast, she asks for a sign to cancel. Nicholas, returning from Dublin, travels west to see Mr. Gore, the poet who wrote the winning poem for the painting.
Arriving at the Gores' home soon after the wedding, Nicholas finds Margaret and Sean; he stays while Muiris is fetched. Sean suddenly begins to speak and stands; the family rejoices, inviting Nicholas to stay. They share a meal and dance again.
A budding connection forms between Nicholas and Isabel. Margaret senses trouble and blocks their letters; she burns the first, tosses the second into the sea, and buries the third. Nicholas writes more, and Muiris's winning love poem hints that four letters can unite two loves.
On a beach, Nicholas finds Isabel; as they embrace, the ghosts of their families appear on either side. The painting William created to depict this moment is finally shown.
