Years after complete antibiotic resistance has resulted in the loss of most human life on earth, Kit and Crevan eke out an existence on a remote island. Under a collapsing castle, they spend their days in an underground bunker packed with emergency stores, venturing out only at night.

They are safe. One evening a woman washes ashore, nearly drowned. Crevan wants to keep her alive, but Kit isn't so sure.

The new arrival will implode Kit and Crevan's world with dire and fatal consequences, churning up the waters of the past and unearthing secrets they have kept from each other and from themselves. Who is really in control - and what are they both capable of doing to protect their haven?