Neffy is a young woman, running away from grief and guilt, and the one big mistake that has derailed her career. When she answers the call to volunteer in a controlled vaccine trial, it offers her a way to pay off her many debts, and, perhaps, to make up for the past. But when the London streets below her window fall silent, and all external communications cease, only Neffy and four other volunteers remain in the unit. With food running out, and a growing sense that the strangers she is with may be holding back secrets, Neffy has questions that non one can answer. Does safety lie inside or beyond the unit? And who, or what, is out there? While she weighs up her choices, she is introduced to a pioneering and controversial technology which allows her to revisit memories from her life before: a childhood divided between her enigmatic mother and her father in his small hotel in Greece. Intoxicated by the freedom of the past, and the chance to reunite with those she loves, she increasingly turns away from her perilous present. But, in this new world, where survival rests on the bond between strangers, is she jeopardising any chance of a future?