In the not-too-distant future, one of scientists' worst fears has been realized: antibiotics have become obsolete, and a pandemic virus nearly wipes out all of humanity. What's left of the world has been divided between those selected to live illness-free within a man-made community quarantine and the outcasts abandoned outside to face uncertain survival. In the wake of an unraveling society, four teens struggle to determine their place in a world that has become warped by the decisions of the previous generation.

Cat, who has grown up privileged within the walls of The Community; Wren, a rebellious survivor on the outside; and Abel and Ryder, the two orphan boys who love them. As their paths intersect, the shocking truth surrounding the so-called vaccine that made initial survival possible is revealed, and these four teens must face the moral dilemma: How far would you go to save the ones you hold most dear?