In a world where a deadly zombie virus has infected mankind, a single cure has been found. The cure, a treatment called the "Return Protein," stays the effects of the virus in its host. With daily injections, the "Returned" are able to live as though they were never bitten, despite the virus still coursing through their veins. When it is discovered that the protein stock is running low, chaos erupts. Returned who run out of the protein turn to zombies and wreak havoc, protestors turn to murderers as they try to rid the streets of the Returned, and right in the middle of it all are Alex and Kate. Kate is a leading doctor in the field of zombie viruses and Alex is a musician with a dark secret - he is a Returned. As death and fear run rampant, Alex's secret is revealed, and he and Kate must fight for a chance to live before he becomes a zombie.