After hijacking a balloon from a Confederate camp, a band of five northern prisoners escapes the American Civil War. Seven thousand miles later, they drop from the clouds onto an uncharted volcanic island in the Pacific. Through teamwork, scientific knowledge, engineering, and perseverance, they endeavour to build a colony from scratch. But this island of abundant resources has its secrets. The castaways discover they are not alone. A shadowy, yet familiar, agent of their unfathomable fate is watching.