Mo Kane is a friendly tour guide in the city of Grahwood, Wessing Territory, who finds out that her personal history is much more complicated than she ever knew. In this first story of the series, Mo discovers what she thinks is a clue to finding the people responsible for her father's recent death. As she tries to puzzle out what it means, she meets an unusual traveler named Kyle Greenhand, who reveals to her that the territory boundaries, called World Rims, are failing. That means neighbors from the magical realms in Semweisse, the middle territory, could make their way into mundane Wessing, where magic is distrusted and magic users even more so.

She and Kyle are almost killed by a group of assassins who have passed through the World Rim, and they seek help first from Mo's sister, Janika, who is Captain of the city guard, and then from an old friend of their father's, Sorcha. Mo discovers, however, that her friends — new and old — are not exactly who she thinks they are. And the clue that may have given her answers about her father's death has left a mark on her that leads a dangerous demon's familiar directly to Mo and her friends.