The darkness isn't empty. It's hungry.

At the edge of the City of the Void, a massive chasm extends miles into the earth, its treacherous terrain overrun with vicious monsters and carnivorous plants. For orphaned best friends Petra and Jade, guiding treasure-seeking tourists down into the Void is the only way to earn enough to pull themselves up out of the slums for good.

Petra prefers to play it safe and take jobs only in the Void's upper levels, where the dangers are better understood, while Jade wants to risk a descent to the deepest and most mysterious Sixth Layer. Because the deeper they go, the better the payout, and the sooner their dreams can become reality. Their friendship is Petra's whole world, and Jade's approval means everything—so Petra agrees to do it Jade's way.

When their job goes wrong and Jade is lost in the Void, Petra must plunge deeper than she's ever dared to save her friend. But she doesn't know the truth of the Void . . . or what really waits for her in its depths.