Marguerite and Auguste walk along the shore, despairing at the prospect of raising a child in their isolation. Marguerite admits she secretly hopes to miscarry, and confesses as much to Damienne, who reminds her that many mothers work and toil through pregnancy. As Marguerite feels the child quicken and kick, she begins dreaming of her son as a prince of the island, and both she and Auguste come to love the unborn child. Damienne tells them that Marguerite's own mother died giving birth to her at twenty—Marguerite's current age—and Auguste vows he could not forgive himself if Marguerite died.

By late September the island's vegetation dies, and in October the seabirds depart en masse. The next day brings sudden, premature snow that does not relent. The three bundle in layers, heat stones for warmth, and shelter inside the cave. While gathering wood, Marguerite and Auguste encounter a striking white fox that vanishes, leaving tracks like a vision of the wild winter.

In early December a three-day storm buries the cave's entrance. They huddle in darkness without candles, eating salted meat and drinking the last wine; Damienne urges Marguerite to recite Marot's psalms for comfort. When the wind dies, Auguste chops them out into a transformed white world. The winter proves longer and colder than any they have known: the sea freezes solid, joining the island to the mainland, but they are too weak to cross. Provisions dwindle, and they sleep through long nights.

Marguerite wakes from a dream with cramps but does not bleed; the child kicks on. Then Auguste falls gravely ill with a swollen, tender belly, vomiting black bile and burning with fever. Quince preserves briefly seem to revive him, but he weakens steadily. Sensing his end, he begs Marguerite's forgiveness for tempting her aboard the ship and insists she learn to load and fire the arquebus. He drills her repeatedly through the motions of loading, aiming, and firing, telling her she must defend herself, hunt, and live without him. Marguerite reluctantly promises, pleading for him to rest and wake again.