Jas Harrington, chief security officer of the starship, Galathea, has returned to Earth after defeating the aliens called Shadows, only to find they're invading her home planet.

Everywhere she turns, the aliens are walking among Earth's population unnoticed. They've infiltrated the government and they're building Shadow traps, ready to launch a full-scale assault.

As Jas tries to find a way to stop the alien invasion, she stumbles across Earth's underworld subculture. She needs the underworlders' help, but they hate the human society that's rejected them, and they refuse. In fact, they cross Jas at every turn.

She must prove that Earth is under threat and make the government fight back. She must overcome the obstacles the underworlders put in her way. If she doesn't succeed, the Shadow invasion will succeed and they'll destroy humanity forever.