Neffy is a young woman running away from grief and guilt and the one big mistake that has cost her 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 ...