A group of anarchists are under surveillance by Scotland Yard in Chesterton's hugely popular metaphysical thriller.

The Supreme Anarchists Council is dedicated to overthrowing the world order. To keep their identities a secret, each of them has been named a day of the week. Gabriel Syme, an eccentric poet, is recruited by Scotland Yard to infiltrate the group. He tracks down the six men and manages to win a place on the council.

But in a bizarre and surreal twist of events, Syme realises that five of the six members are not at all what they seem...