Henry Adams explores political intrigue in late nineteenth-century Washington, DC. By inserting the character of Madeleine Lee (a wealthy widow from New York) into the nation's capital, Adams reveals the continuing post-Civil War "North versus South" conflicts in US politics.

Madeleine is fascinated by power and hopes to play an informal but influential role on the national scene. Madeleine and her sister, Sybil Ross, take up residency and begin having weekly parties in a home near the White House.

At the Capitol, Madeleine observes the sessions of Congress. Soon, romantic links develop between Madeleine and two distinct political and regional rivals: John Carrington of Virginia and Silas Ratcliffe of Illinois.

Carrington, working assiduously to overcome his family's Confederate past and gain a foothold in national politics, seems more genuine in his affection for Madeleine. Ratcliffe, a senator with aspirations to become Secretary of State, is more successful in his courtship, however; his engagement to Madeleine seems inevitable.

A number of minor characters and subplots round out the Washington scene. Madeleine, already friends with Senator Clinton of New York, gets to know Lord Skye, the British ambassador, and his wife. These relationships further develop during the group's trip to Mount Vernon, Virginia—the former plantation of George Washington.

The political machinations within the novel include Ratcliffe's efforts to become a cabinet official, his opponents' maneuverings to block his appointment, and his ultimate goal to become president. In addition, there are investigations into Ratcliffe's corrupt business transactions owing to the recent death of a lobbyist named Samuel Baker. Ratcliffe temporarily outmaneuvers Carrington by getting him appointed to a job in Mexico, but Carrington manages to expose his rival's illegal dealings to Madeleine. She then refuses Ratcliffe's proposal. Ratcliffe then makes a scene during a dinner at the Skyes' home, getting into a violent altercation with an elderly Bulgarian diplomat.

Ultimately, Madeleine leaves Washington to take a trip abroad.