Over four billion are dead, missing, or one of them: infected by the omega virus. Known as o-dogs, they are hyper violent and no longer feel pain. All they want to do is tear your face off and eat it. For the citizens of Camp Pendleton, life is about white knuckled survival behind a border of landmines that offer a thin membrane of sanctuary. But then the base is attacked by weaponized o-dogs, and a band of soldiers known as the Four Horsemen realize there are men behind the virus. Men behind the destruction of cities, countries, and continents. A secret society who call themselves the Shepherds. Who rule the remains of humankind with merciless regard. And who will pay for their crimes.