In the shadow of the giant-the three-mile-tall alien that dropped down, seemingly dead, just outside of town-Little Springs continues to grow: 200,000 people and still expanding rapidly. Crisis looms as they come to realize there is not enough water for all of them. A tech industry titan decides to dam a river and pipe its water into the city, which sparks off a quickly growing protest. The dam is to be built on the historic site of a Lakota massacre at the hands of the U.S. army. Sheriff David Blunt is tasked with mediating the conflict, an assignment that becomes impossible when a protester turns up dead-murdered, David believes.

Meanwhile, scientist Sunny Lee is on the verge of a breakthrough to understanding the truth of the giant. Except, to unlock its mysteries, she'll have to venture into the giant itself and risk touching off a cataclysm. All the while, worrying omens appear, indicating that the blade stabbed through the giant is spreading its infection-an alien life form with its own dark agenda.