The Man Who Was Thursday: A Nightmare was written by G.K. Chesterton and published in 1908.
Syme infiltrates a secret meeting of anarchists and becomes Thursday, one of the seven members of the Central Anarchist Council. He soon learns, however, that he is not the only one in disguise, and the nightmare begins...The Man Who Was Thursday has a Mission plot, although the final confrontation with the Antagonist is rather a bizarre one.