As another violent storm closes in, Rowan warns Orly that the lower area beneath the vault will soon flood, hoping he and Dominic will understand that anything hidden there must be moved. Alone, Rowan resolves to act rather than remain passive while the island and the vault deteriorate.

Rowan then follows a distressed sound through the lighthouse and finds Fen in the bathroom, overwhelmed by severe period pain and short on supplies. While Rowan comforts her, Fen reveals that before Rowan arrived she feared she was pregnant. Fen presses Rowan to learn who the father might have been, and Rowan realizes the answer is Hank. Rowan reassures Fen that Hank is a manipulative narcissist who exploits people, making clear that Fen is not to blame for what happened.

Later, Rowan tells Dominic and Orly that Fen is too unwell to help, and the three make what Dominic says will be their final trip to the vault. Rowan and Dominic wade through freezing, rising water to salvage as many seed containers as they can, loading them onto a floating pallet. As they work, Rowan thinks about Hank imprisoned below and about whether Dominic intends to let him drown.

When a second crack opens in the vault wall and water pours in faster, Dominic orders a retreat. While they struggle the pallet back through the tunnel, Rowan urges Dominic to talk to Raff and Fen and, if he does not know what to say, at least to listen. By the time they reach the tunnel mouth, Rowan has decided that however terrible Hank is, she cannot allow him to die trapped below.

Outside in the battering rain, Dominic kisses Rowan with the feeling of a farewell. Rowan tells him she cannot leave Hank to die, and Dominic admits he understands. He finally reveals why Hank was imprisoned: Hank had an affair with Fen, and when something went wrong he tried to kill her by holding her underwater. Dominic says he hid Hank because he could not trust Rowan not to free him and because he needed to protect Fen. Rowan insists that if Dominic chooses to let Hank drown and makes her complicit, any future between them will be destroyed, but Dominic replies that he is willing to do it if that is what protecting his daughter requires.