In a post-zombie world, where the infected live normal lives, their retroviral drug is running out.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” which stays the effects of the virus in its host. With injections every 36 hours, the “Returned” are able to live as though they were never bit, despite the virus still coursing through their veins. When it is discovered that the protein stock is running low, chaos hits the streets. Returned who run out of the protein turn to zombies and wreak havoc, protesters 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.