Lily Grim's life is a mystery.

She has lived with her guardian Gabriel, in their rundown second-hand shop in the City of Undone, for as long as she can remember.

For years, the city-dwellers have lived in uneasy discord with The Others - a community of wanderers forced to shelter within the city walls, after they were driven from their nomadic camps in the wilderness. But Undone is a dark and dangerous place to live, especially if you're an Other: feared for their special gifts, they are persecuted by the cruel Master of the City, and taken to the Ring - a prison from which few ever return.

When the Master captures Gabriel and throws him into the Ring, Lily is saved by a young Other boy called Dekka. He introduces her to a whole Otherworld that exists beneath the City of Undone. To her astonishment Lily discovers she is an Other, too - with powerful gifts - and is now in grave danger: because the Master wants her dead. But why?

Can Lily find answers about who she is, and where she's from. And can the new friends rescue Gabriel, before it's too late?