Promicin -- which kills half of those who dare to inject it and grants paranormal abilities to those who survive -- is spreading across the globe and threatening to plunge the entire world into chaos.

One year has passed since Jordan Collier and his followers seized control of Seattle and renamed it Promise City. U.S. armed forces have surrounded Seattle, and each day brings Collier and his Promicin-Positive Movement closer to all-out war with the world's greatest military superpower.

However, the real threats are the Marked -- agents from the future whose identities are encoded into body-hijacking nanites. They were sent back to thwart the efforts of the 4400. The last three surviving Marked lurk in the shadows, working in secret as they prepare to deliver a deathblow to the planet.

Caught in the crossfire are NTAC agents Tom Baldwin and Diana Skouris. His son, Kyle, and her thirteen-year-old adopted daughter, Maia, are both more loyal to Jordan's movement than to them. And when the standoff between Collier and the U.S. military explodes into open conflict, Tom, Diana, and fellow agents wind up outnumbered and outgunned.

In the end, the fate of all mankind will rest in the hands of one man: Tom Baldwin.