The novel is told via the framing device of a manuscript found centuries after the action takes place and footnotes by a scholar, Anthony Meredith, circa 2600 AD or 419 B.O.M. (the Brotherhood of Man). Jack London writes at two levels, sporadically having Meredith correcting the errors of Avis Everhard through his own future prism, while at the same time exposing the often incomplete understanding of this distant future perspective. Meredith's introduction also reveals that the protagonist's efforts will fail, giving the work an air of foreordained tragedy.
The story proper begins with Avis Everhard, a daughter of a renowned physicist, John Cunningham, and future wife of socialist Ernest Everhard. At first, Avis Everhard does not agree with Ernest's assertion that the whole contemporary social system is based on exploitation of labour. She proceeds to investigate the conditions the workers live in, and those terrible conditions make her change her mind and accept Ernest's worldview. Similarly, Bishop Morehouse does not initially believe in the horrors described by Ernest but then becomes convinced of their truth and is confined to a madhouse because of his new views.
The story covers the years 1912 through 1932 in which the Oligarchy (or "Iron Heel") arises in the United States. Japan conquers East Asia and creates its own empire, India gains independence, and Europe becomes socialist. Canada, Mexico, and Cuba form their own Oligarchies and are aligned with the U.S. (London remains silent as to events transpiring in the rest of the world.)
In North America, the Oligarchy maintains power for three centuries until the Revolution succeeds and ushers in the Brotherhood of Man. During the years of the novel, the First Revolt is described and preparations for the Second Revolt are discussed. From the perspective of Everhard, the imminent Second Revolt is sure to succeed. Given Meredith's frame story, the reader knows that Ernest Everhard's hopes will go unfulfilled until centuries after his death.
The Oligarchy is the largest monopoly of trusts (or robber barons) who manage to squeeze out the middle class by bankrupting most small to mid-sized business as well as reducing all farmers to effective serfdom. This Oligarchy maintains power through a "labor caste" and the Mercenaries. Laborers in essential industries like steel and rail are elevated and given decent wages, housing, and education. Indeed, the tragic turn in the novel (and Jack London's core warning to his contemporaries) is the treachery of these favored unions which break with the other unions and side with the Oligarchy. Further, a second, military caste is formed: the Mercenaries. The Mercenaries are officially the army of the US but are in fact in the employ of the Oligarchs.
Asgard is the name of a fictional wonder-city, constructed by the Oligarchy to be admired and appreciated as well as lived in. Thousands of proletarians live in terrible poverty there, and are used whenever a public work needs to be completed, such as the building of a levee or a canal.
