As the storm batters Shearwater, Dominic races Rowan by boat toward the collapsing seed vault. Rowan sees South Beach already swallowed by the sea and the cliffs actively crumbling, which convinces her the vault may soon be lost entirely. Dominic runs for the hilltop hatch with tools, while Rowan chooses the flooded tunnel below because she fears Orly may still be trapped inside.

Rowan forces herself through the water despite her terror of drowning and searches the dark vault. When she reaches the shaft chamber, she realizes the heavy door may trap her inside once it closes, but she enters anyway because she cannot abandon Orly if there is any chance he is there. In the dark, Orly answers her, and Rowan finds him sitting on Hank’s camper bed and embraces him.

Orly admits he released Hank, and Rowan realizes Hank abandoned the boy underground. Orly also learns that Rowan discovered what he did with the seed crates. He explains that he chose unusual, unwanted plant species because humans will improvise to survive, but plants and the animals that depend on them will vanish unless someone protects them; he adds that he saved some rice and wheat too.

Rowan tells Orly they must escape through the hatch because Dominic is opening it from above. They make their way to the ladder in near darkness, but the hatch glass cracks overhead and Rowan warns Orly to shield his face from the falling shards. The climb is slow and dangerous because the rungs are slippery and the shaft is already taking on water.

Halfway up, a new crack opens in the wall and a surge of water pours onto them. Orly screams, and Rowan pins him to the ladder so he will not be knocked free, then forces them onward as the shaft begins filling faster. Near the top, Orly hears Dominic calling through the opening, and father and son shout to each other while Rowan watches the rising water and waits for Dominic to get them out.