Faced with the approach of an unstoppable army, the people of the Citadel are forced to flee. While most of the population attempts to escape along the southern waterways, the group of newly possessed friends choose a more dangerous path.

Guided by visions, the possessed friends enter the Theleram, an expansive network of caves, stretching hundreds of miles beneath the rainforest. The visions direct them to the ruins of the ancient city of Semilae, where a hidden library lies.

Meanwhile, Raelyn, the willful demon who brought about the fall of the Citadel, struggles to make a home for herself in Derregain, the largest remaining human city. The Demon Queen has placed a price on her head, and many powerful demons are interested in collecting.

But Derregain itself is struggling, as sickness begins to spread through city streets. Raelyn knows the plague is demonic in origin, but will she survive long enough to share her knowledge?