Jo and the rest of the pioneers have only just made peace with the Sorrow, inhabitants of the planet Tau Ceti E by agreeing to return home to Earth when devastating news strikes: Earth itself has been destroyed. Tau Ceti E is now the only place left to the pioneers and the scant population of Earth who managed to escape the planet. Upon the arrival of Jo’s grandfather and the rest of the survivors, the hard-won relationship with the Sorrow seems to quickly dissolve, and Jo finds herself caught in between loyalty to her family—and the promises she made to the Sorrow leaders. But when a threat arises that could potentially wipe out both Sorrow and human life, Jo must find a way to unite warring factions before both sides are lost forever.