There are seven members of the radical Central Anarchist Council who, for security purposes, name themselves after the days of the week - Sunday, Monday, etc. However, the turn of events soon cast doubt upon their true identities, for the man who was Thursday is not the impassioned young poet he pretends to be, but rather a member of Scotland Yard's anti-terrorist squad of secret detectives. Who and what are the true identities of the other days of the week? Chesterton unwinds the mysterious entanglements in his own inventive and lively way and then escalates the mounting nightmare of paradox and surprise, culminating in a shocking revelation. He probes the mysteries of behavior and belief in an all too human world.