Jean Alfonse helps a frantic Marguerite to the cabin and advises her to beg Roberval for mercy. Damienne is horrified, but Marguerite refuses to repent. Marguerite spends the day imagining brutal punishments, certain Roberval will hang Auguste or kill them both. When Roberval returns, he cheerfully announces he has bullied Cartier into agreeing to sail with them to Charlesbourg-Royal. He orders Auguste's food sent below and tries to force Marguerite to drink wine; she refuses defiantly and is dismissed.

At dawn, Marguerite goes on deck and discovers that Cartier's three ships have vanished, having cut their ropes and slipped away in the night. Roberval, stunned, accuses the night watch of sleeping, but the captain explains Cartier cut his moorings. Roberval vows Cartier will hang in France, then rallies the colonists by promising the riches of New France will not be shared. The wind has died, however, leaving the ships becalmed.

Roberval retreats to the cabin and works on his logs, ignoring Marguerite. Jean Alfonse requests leave to chart more islands; Roberval grants it and orders Auguste brought up from the hold. Pale and silent, Auguste is unshackled. Roberval reproaches him for betraying his trust, but Auguste refuses to apologize and tells Roberval to do as he likes but not abuse Marguerite. Marguerite kneels and begs for Auguste's forgiveness.

Roberval pronounces his sentence: because the two are so attached, he will leave them together on an island that Jean Alfonse will find. They may take provisions and weapons. Marguerite, horrified, realizes this is a slow death sentence. When she pleads that Damienne is innocent, Roberval coldly says he does not want the nurse and exiles her too. Finally, with mocking sweetness, Roberval hands Auguste his cittern, telling him to play it if he can.