Marguerite devotes herself to physical labor to serve Damienne, hunting birds with her arquebus, fishing, and gathering wood, while Damienne tends fire, butchers, and preserves food. Marguerite measures her remaining time by her dwindling powder supply but conceals this worry from Damienne. By night, she dreams of Auguste being carried off by birds or transformed into one, and she hunts in waking hours partly to kill what tormented him in her dreams.

Through summer, the two women adapt resourcefully: Damienne harvests salt from evaporated seawater, sharpens their knife with smooth stones, mends clothing, and keeps house. They dry the island's bitter berries like raisins, decorate their cave with small white flowers, and lay autumn leaves on their altar to the Virgin. In the evenings Marguerite reads scripture aloud, including the parable of the lost coin, and Damienne, transformed by hardship into someone braver and wiser, hopes to return like that coin. Marguerite declares she now understands what it is to be a man—to have one's way—though Damienne questions whether that is right.

For the first time, Damienne speaks of her own past: three older married sisters, a younger brother, a mother who died, and a father too poor to feed her, which is why an aunt brought her into Marguerite's family's household. She rose from kitchen scullery to serve Marguerite's mother and then Marguerite herself, whom she calls her child.

Disaster strikes when the well-sharpened knife slices Damienne's right palm as she cleans fish. Marguerite staunches the bleeding, but Damienne's fingers go numb and the wound festers. Within days fever and infection consume her. Damienne accepts that she will die and prays for a peaceful end, while Marguerite secretly begs her to stay. Recognizing her selfishness, Marguerite recites a psalm about clean hands and a pure heart; Damienne turns the blessing back onto Marguerite, calling her strong, and dies quietly affirming God's goodness.

Marguerite closes Damienne's eyes, wraps her in a sheet, and buries her in the third trunk. She scatters gold autumn leaves on the grave and prays to the Virgin to welcome Damienne—the woman who was truly her mother—into heaven.