As the survivors continue to seek stability in their lives, forces both inside and outside the fort walls move them toward a final, climactic conflict between the living and the dead. Jenni, Katie and the others discover that they are not alone, that there is another enclave of survivors whose leaders plan to take over the fort. Faced with a series of difficult decisions, each choice they make could lead to the deaths of those they love or, if not careful, their own demise. Meanwhile, an army of the dead is descending on the fort. Soon, the living will face their ultimate fear... ...a siege by the dead. But they will fight to the end to survive... As the world dies.