The fourth and final book in The Circle Opens quartet. Tris finds Tharios oppressive and disturbing. The townsfolk are obsessed with protocol - to the extent that they have an entire underclass who seem to be invisible, never seen, never spoken of. When a series of brutal murders disturb the fragile peace of the city, she is shocked by the city-fathers' attitude - surely they need to do more than tidy these crimes away? Her only help is Keth, a reluctant mage-student who shares her lightning-magic after being near-paralysed by a lightning strike. His skill at glassblowing has been all but destroyed and he bitterly resents this magic he cannot understand or control. But when one of his dearest friends is murdered, he and Tris realize that his power may the one thing that can entrap the killer...