Charlie Meiklejohn and Constance Leidl probe a mystery whose origins lie beyond the Earth. A series of arson attacks—seemingly unrelated—are destroying old empty buildings across the country, and costing insurance companies dearly. The problem proves not so much to trace the perpetrator, but to understand and prevent the phenomenon which he has been tracking and trying to stamp out for five years: a series of outbreaks of sudden, murderous insanity, each one centered on a remote, deserted building.