Separated from her family in the chaos of an alien invasion, Maddy Walker finds herself an unwitting soldier of the invading Raider army. Bonded to the Raiders, Maddy and her squad are forced to help destroy the last of the human race. Humans survive in the Lifeline - a number of bases built underground across the world, connected by the Lifeline Link. During a mission to get inside a Lifeline base, the bond with the Raiders is broken and Maddy and her squad are plunged back into their humanity. No longer connected to the Raiders or trusted by the human rebels, it is up to Maddy and her friends to find out where they belong in this new world. As for the Raiders, they are about to find out just how dangerous their creations can be.