David Weinberg, a seasoned lawyer in his fifties, and his much younger wife Alexis Chandler Weinberg navigate a torrential downpour to reach the last ferry to their private island. They spot an injured Young Man by the road and, despite reluctance, give him a ride to the nearest town. After missing the ferry, the couple checks into a motel and catch the next day’s boat, with the unnamed young man also on board, though they never directly meet him.
The trip underscores a strained seven-year marriage, marked by miscommunication and missed opportunities. To mend fences, David plans a romantic sailing excursion, but a creeping fogbank causes them to run aground. On the shore they discover the young man camping nearby and invite him to share his fire. David enlists his help to unground the sailboat and invites him into their home.
That evening, Alexis dreams she has offered the young man a blanket and that her husband has attacked her in a jealous rage. In the morning, the couple learns that the young man has already made them a lovely breakfast, delivered by David. He is invited to stay for dinner as part of a playful cooking challenge, while David steps out to play golf. The two grow closer as they pass time together—drinking whiskey, dressing up in the boathouse for fun, and exchanging stories. The young man describes himself as a poet who cannot write, showing Alexis his work in several different handwritings, and moves her to dictate a dark poem about drowning.
A wild mushroom hunting expedition follows, during which Alexis saves the young man from consuming a lethal mushroom and demonstrates how to tell the difference between a deadly variety and a nearly identical, aphrodisiac one. After a failed attempt to persuade Alexis to eat the aphrodisiac mushroom, the trio returns home, and the young man receives an apology from David.
David returns from the golf course claiming illness, but regains enough strength to prepare dinner for the trio. Their plan to return the young man to town is derailed when the boat dies mid-journey, forcing him to stay another night, much to his apparent displeasure. The next morning, a confrontation erupts between David and Alexis, and the young man slips away to hide in the shed, pursued by David into the woods. When Alexis confronts him there, she declares that their relationship is finished, only to find the young man waiting nearby.
He seduces Alexis as he urges her to eat another mushroom, and this time she does not intervene. A funeral follows, and the young man’s poem—written in Alexis’ handwriting and signed in her name—is read as if it were a suicide note. David returns to the island by boat, strips naked, and swims ashore in icy waters, washing away his old life.
Some time later, a hooded figure arrives at the house, kissing David. It turns out to be the young man, and the two lovers reveal that Alexis’ death was a calculated plan shared by them. The unsettling conclusion leaves a sense of complicated desire and a bond forged in secrecy, with the island lingering as a silent witness to a relationship that reshaped all their lives.
