In a reflective opening, Rowan tries to use her mother’s final days to understand the past. Her mother finally reveals that the family lived on the boat because a flood destroyed their home and they had no money or refuge, not because they chose an adventurous life. Rowan presses her about leaving children alone and forcing thirteen-year-old Rowan to care for the others, but her mother offers no real accountability, and Rowan realizes she will not receive the forgiveness or clarity she hoped for.

Not long afterward, Rowan’s mother dies with Liv and Jay beside the bed. In that moment, Rowan releases some of the blame she has carried over River’s death and reinterprets her family’s history: the dangerous life on the boat was shaped by a collapsing world, not simply by one mother’s selfishness. Rowan concludes that more children will be lost to floods and disaster, but she is certain they will not be her children.

The narrative then returns to the whale rescue on Shearwater. The channels the group dug finally matter when an extreme tide drags the stranded mother whale back into the sea, where she reunites with her calf and swims away. The survival of mother and calf shakes Rowan’s fatalism, and when Dominic gathers his children, Rowan decides she will not stand apart from the love being offered to her. Later, after Dominic ferries everyone home on the quad bike, Rowan tells him she wants a shared future with him, including a workshop big enough for both of them, and Dominic answers that he would go anywhere with her. They fall asleep together at the lighthouse, though Rowan is briefly unsettled by the possibility that Dominic’s murmured declaration of love might be meant for his dead wife.

The next morning, Orly wakes Rowan and Dominic to resume moving seeds from the failing vault. Raff’s arm has swollen and he stays behind, while the others keep working in exhaustion. During the salvage, Rowan notices increasingly strange behavior: Orly repeatedly talks to himself in the same corner of the vault, Fen is tense, and Rowan overhears Fen telling Dominic that what they are doing is a violation for which they could all be punished. Dominic dismisses Fen’s worry, but Rowan becomes convinced the family is hiding something from her.

That night, Rowan pieces together Dominic’s earlier story. If the communications were sabotaged before the researchers left, then Hank could not have departed on the ship as Dominic claimed; Hank must have remained on the island with the others. Rowan wakes Raff and learns that Alex died by hanging, which makes Rowan realize the blood she once saw in Hank’s cabin must have belonged to someone else. The next day she secretly follows Dominic back into the vault, finds the supposedly unused air-shaft door ajar, and discovers that it leads to a hidden lower room stocked with food and supplies. There, alive and staring at her in shock, is Hank Jones.