Gabriel Syme confronts anarchist Lucien Gregory giving a speech. After an argument, Gregory tempts Gabriel to join him in an underground meeting of anarchists and the election to select a new Thursday on the council of Days.
Our detective goes undercover as Thursday in the anarchist Council of Days. He is introduced to their leader, the powerful and frightening President Sunday.
Barely escaping the council meeting unscathed, Gabriel is followed through the streets of London by a decrepit old anarchist, Professor de Worms.
Now joined by two other detectives, Gabriel travels to France to foil an assassination plot to be carried out by the Marquis de St. Eustache.
The team of detectives seek answers from the only man that can provide them, the elusive President Sunday.