After years of living beneath the threat of an oncoming war, Jace and his younger sister, Kaia, found refuge in the distant Mairua Isles with the chance to begin again.

Then a familiar face from his childhood returns. A bloodthirsty monster he once trusted—and one he never quite managed to forget. But before he can decide what to make of her return, Kaia disappears.

Finding herself trapped in a strange world surrounded by unfamiliar faces and creatures she knows little about, Kaia soon discovers that the realm holds far more than the terrors she was warned of—and that some of its secrets have been waiting a very long time to be found.

Desperate to save the only family he has left, Jace ventures into Po—the realm of darkness—with his natural enemy. But as they face the horrors lurking within, he finds himself struggling with a growing desire for the very one he should despise.

In a realm where nothing is what it seems, how far will Jace go to save his sister—and what will he lose along the way?