A bewildering modern fable in which the characters continually unfold, and not without humor, to their most unspeakable fears. Gabriel Syme, the protagonist of the story, comes a day by Saffron Park and meets Lucian Gregory, a false fire-haired anarchist who speaks in the manner of the biblical prophets in the midst of general derision. However, this false anarchist turns out to be a true anarchist and, his pride wounded by the doubts of Syme, decides to teach the bowels of the vast criminal organization, after make Syme promise not to reveal anything to anyone, not even the police, about what he would see that nigh. Then Syme, after promising this, in turn requires that the promise is mutual and then, proves to be a policeman from Scotland Yard, that for the same promise is incapable of requesting help, but is also protected and nobody will know that he is a policeman. In this way he becomes involved in a serie of events, several of them caused by himself, which led to his appointment as one of the principal officers within the organization. Seven are the days of the week and seven positions of major anarchists who just take their names of the days, including the ineffable "Sunday", the boss, wide and fat as it can only be the world or the universe.
Chesterton puts us several traps in this novel, one of which (perhaps the first) is to make us believe that we have a detective story, because if it is true that there is a mystery, it derives more toward the realm of ideas, towards an allegorical struggle between order and chaos that is dissolved as both sides become indistinguishable, especially in an atmosphere of burlesque that Syme, the "Thursday", only coming out at the end. All anarchists, one after another, revealing that they actually belong to the police, even “Sunday”, who will lead the six members of the farce toward a final performance, which will come to light the essence of each from their own costume, and eventually lead to a phantasmagoria: the ambiguous awakening from a nightmare.