"They only come at night, when the Star fades" Lark Ainsley escapes the Iron Wood to search for her brother, only to find herself captured and imprisoned in an underground metropolis. Powerful magic protects the city of Lethe, providing sanctuary from the Empty Ones, monsters who hunger for human flesh.

Lark returns to the city within the wall, only to discover that mass rebellion has broken out against the Institute. She is even more shocked to find that her brother Caesar is the leader of the revolution. Bur rebellion is not the only problem. The city is running out of magic and once it's gone, nothing can protect the citizens from the shadows that lurk outside the wall. Nothing, except Lark.