For twelve years Aina and Whitney have been in exile on an island for a crime they committed together, tethered to a croft by pills they take for survival every eight hours. They've kept busy - Aina with her garden, her jigsaw, her music; Whitney with his sculptures and maps - but something is not right. Shipwrecks have begun washing up, supply drops have stopped and on the day their punishment is meant to end, the Warden does not come. Instead a sheep appears; but sheep can't swim.