From the ashes of a devastated Woodbury, Georgia, come two opposing camps of ragtag survivors. Underground, in the labyrinth of ancient tunnels and mine shafts, Lilly Caul and her motley crew of senior citizens, misfits and children struggle to build a new life. But a secret ambition still burns inside her: She wants her beloved town of Woodbury back from the plague of walkers and now the only thing that stands in her way currently roams the wasted backwaters of Georgia.
Way out in the hinterlands, amidst the rising tide of walkers pushing in from all directions, the psychotic Reverend Jeremiah Garlitz rebuilds his army of followers with a diabolical secret weapon. Intending to destroy Lilly and her crew, the very people who vanquished his cultish church, he now has the means to bring a special brand of hell down upon the tunnel dwellers.
The final confrontation between these two human factions unleashes an unthinkable weapon forged from the monstrous hordes of undead, perfected by a madman and soaked in the blood of innocents.