In Edwardian London, Scotland Yard police detective Gabriel Syme is inducted into a secret anti-anarchist taskforce. Going undercover posing as an avowed anarchist, Syme is soon introduced to a secret society of anarchists. The society has secrets of its own, and nobody is entirely sure of anyone's motives. G.K. Chesteron's fascinating metaphysical thriller had been adapted for stage and radio on a number of occasions.