The novel unfolds as an intimate monologue addressed to a figure named Jeffers. The narrator, M, begins by recalling an experience on a train leaving Paris years earlier: She encountered a devil-like man, bloated and yellow-eyed, who pursued her from carriage to carriage while fondling a young girl as other passengers looked away. M chose not to intervene, and she links this moral failure to the disasters that followed.
Earlier that same day, M had walked along the Seine at dawn and come upon signs for an exhibition by a painter she refers to only as L. Standing alone before his self-portraits and landscapes, she experienced an overwhelming sensation paired with a phrase: "I am here." The encounter left her feeling as though she had fallen out of the frame of her own life.
In the years that followed, M's first marriage collapsed. Her first husband took their daughter Justine away for a year, calling M "that terrible woman," and M reached a point so desperate she attempted to end her own life. She survived, she says, because mothers cannot truly die. Eventually she met Tony, a large, quiet, dark-skinned man adopted as a baby by a marsh family whose adoptive parents drowned in a tidal surge. Together they rebuilt an abandoned cottage on adjacent wasteland into a simple dwelling for visiting artists, which M calls "the second place."
M writes to L, inviting him to the marsh. He accepts but cancels, choosing a friend's island paradise instead. After failed travels and a hospital visit, L writes again. By now, global disruptions have forced Justine and her boyfriend Kurt, a thin, birdlike man, home from Berlin, and M has given them the second place. Then L's fortunes collapse: He has lost his houses and money and asks if there is still space for him. M moves Justine and Kurt into the main house and prepares the second place with renewed hope.
L arrives at a harbor town two hours south, but not alone. He introduces Brett, a ravishing blonde in her late twenties. L is small, wiry, and dapper, with sky-blue eyes, but he hides behind Brett, using her as a shield. On the drive home, Brett runs her fingers through M's grey hair uninvited, offering to color it. At the second place, she calls the cottage "a cabin in the woods, straight out of a horror story."
The next morning, M finds L by an old boat, looking at the marsh. He speaks about his weariness with society and his sense that he has missed something essential about reality. M feels an overpowering kinship with him. L announces he wants to paint portraits and asks if Tony and Justine would sit. M cries out that he should paint her. L replies that he cannot really see her.
Over the following weeks, Brett integrates into the household, spending time with Justine: teaching her to style her hair, mocking her shapeless clothes, and teaching her to sail. Justine blossoms and begins to rebel against Kurt's cautious control, which M recognizes as the same pattern of subtle dominance she experienced with Justine's father. Tony sits for L; the resulting portrait is a tiny miniature that makes Tony look like a toy soldier. L tells M that fathers make painters while mothers, being liars, make writers. He asks why she "plays at being a woman," then leaps onto a tabletop, cavorting and shouting her name. M leaves feeling wounded.
Kurt declares himself a writer and produces a massive manuscript that he reads aloud at an evening gathering for over two hours. L says only that it is far too long. Kurt later tells M that L advised him to break Justine's will and that L intends to destroy M.
The crisis arrives when L finally agrees to paint M. She searches her wardrobe and finds only her wedding dress. She puts it on and hurries through the glade toward the second place, its windows blazing. Tony opens the bedroom window and thunders for her to come back. She runs on. Approaching, she sees L and Brett inside, half-dressed and paint-smeared, painting a mural: a hellish Garden of Eden with obscene flowers, a great snake, and figures of Adam and Eve. She hears them mock "Eve" with details unmistakably targeting M. She turns to flee, but sees Tony's truck taillights disappearing into darkness.
It rains for five days. M sits motionless. On the fifth evening, Tony returns. They look at each other, both knowing something irretrievable has been spent. He holds out his arms; M promises never to make him go away again. He says he went to North Hills, where they first fell in love. That same night, Brett arrives to say L is on the floor, possibly dead. Tony carries L through the mural room without hesitating and drives him to the hospital. L has had a stroke.
L returns frail, stuttering, with blackened eyes and a swollen, useless right hand. Brett decides to leave, taking Kurt to work for her wealthy cousin. Justine surprises M by saying, "Thank God you're my mother," and volunteers to be L's studio assistant. Three weeks later, L makes his first self-portrait, agonizing to hold the brush in his deformed hand. The painting is shockingly crude but alive, establishing the signature dissonance of his late work. He remains hostile to M, telling her all her good has come out in Justine. L's friend Arthur, a debonair man who weeps from compassion, visits and tells M that L is not her responsibility. Arthur and Tony become close friends.
By midsummer, L sleeps during the day and paints at night, producing works that capture something about the marsh M has longed to see expressed. One warm night, M and Justine swim naked in a creek glowing with phosphorescence and afterward spot L scurrying away in the shadows. Later, M watches through curtainless windows as L stands motionless at his easel in moonlight and realizes that a certain kind of stillness is the most perfect form of action.
In their final conversation on a bluff overlooking the marsh, L speaks kindly to M for once. His illness, M understands, released him from identity violently enough to truly see, and what he saw was not death but unreality. He grips her hand, says he knows she will feel better soon, and they say goodbye. M never sees L again.
L leaves a note saying he will try to get to Paris, instructing them to keep the paintings except number seven, which belongs to Justine. He dies in a Paris hotel room of another stroke. His late work sparks a renaissance of his reputation, though his correspondence reveals cruel descriptions of M. Tony and M paint over the mural and give the second place to Justine. The seventh painting depicts two half-forms of light amid darkness striving toward oneness; M believes L painted what he saw the night he glimpsed her and Justine swimming. Justine falls in love with Arthur.
Months later, a letter arrives via a woman named Paulette, who found it unaddressed in the Paris hotel room where L died. L writes that M was right about quite a few things, that he misses her place, that things are "more actual afterward than when they happen," and closes with an apology for what he cost her.