The story begins when Gabriel Syme, a poet and member of a special group of philosophical policemen, attends a secret meeting of anarchists, whose leaders are named for the days of the week, and all of whom are sworn to destroy the world. Their chief is the mysterious Sunday - huge, boisterous, full of vitality, a wild personage who may be a Chestertonian vision of God or nature or both. When Syme, actually an undercover detective, is unexpectedly elected to fill a vacancy on the anarchists' Central Council, the plot takes the first of many surprising twists and turns.