Poet Gabriel Syme believes in the beauty of order and, as such, is recruited by Scotland Yard to an anti-anarchist police corp. While undercover, Syme meets fellow poet Lucian Gregory, a verse writer devoted to disorder, who introduces him to London's anarchist underworld. Just as Gregory is to be elected to the central council, Syme's cover is revealed and he is forced to make a decision that sends the cabal into chaos. Is anyone in this underground faction who or what they seem? Syme suddenly realizes he doesn't have all the answers.

G. K. Chesterton's masterpiece unfolds itself as a marvel of disguises: political parable, detective novel, Edwardian gothic, spy thriller, and metaphysical mystery - a byzantine maze of deception and subterfuge that surprises to this day.

Revised edition: Previously published as The Man Who Was Thursday, a nightmare, this edition of The Man Who Was Thursday, A Nightmare (AmazonClassics Edition) includes editorial revisions.