For decades, the Wardens-a genocidal faction of near-immortal aliens called Echoes- have waged war against all who resist their rule on Earth. Dani survives by scavenging supplies while avoiding the local military and human-hunting Wardens. But when she discovers she's an Echo and not a human, her entire reality crumbles.

When Dani risks her well-being to save a young boy from a violent kidnapping, the rescue makes her already tenuous existence on the fringes of society in Maine even more unstable. Each day forces her to face fragments of past lives she can't remember. She becomes convinced that humanity's only hope lies in uniting the Commonwealth's military and civilian forces against the Wardens' reign.

But to free Earth from the Wardens' grip, Dani must face a ruthless tyrant bent on destroying her and all of humankind-a battle that even her near-immortal heritage might not help her survive.