In the far future, behind the impermeable Shield that protects the city of Seaboard, survivors of humanity's last war are submerged in the Fluid and pass their lives as dreamers, each plugged into a private virtual paradise. Marlo the Computron and her creator, Jed Salt (by now the 271st clone of himself), preserve this sleeping world through science. When Marlo fails, Salt must venture beyond the Shield for the power cell needed to fix her—and to save humanity from extinction. Little does Salt know that the ruined world contains other survivors...and threats.