Benjamin Disraeli (who would become the Prime Minister of England in 1874) wrote Sibyl as a young adult (in 1845). The book is alternately titled The Two Nations because it bespeaks a nation divided between the poor and the affluent. The novel depicts a group of wealthy Englishmen, amusing themselves by eating and drinking at different restaurants and attending horse races.

At the novel's beginning, a group of affluent men are discussing plans to go out to the country. During this trip to Marney Abby, Lord Egremont meets one Walter Gerard, who is a radical conservative eager to rectify the inequality between the wealthy and the poor. His daughter is the charming Sybil, who shares her father's passion for social reform. Egremont also meets the radical Stephen Morley, who seeks to court Sibyl.

Lord Egremont is the younger brother of an English earl (Lord Marley), and he resolves to go undercover to investigate the conditions of the working classes.

Morley and Gerard team up to address members of Parliament and convince them to pass the People's Charter (representative of the contemporary English movement known as "Chartism" in which the reformers advocated for egalitarian principles such as universal suffrage for naturalized citizens, a secret ballot, and the dismissal of property requirements to serve in Parliament). Their mission is not successful, and their cause faces severe opposition by the Tories who have lately come into power in Parliament. Queen Victoria (elected in 1837) retains Whig her ladies-in-waiting (despite protests from the would-be Prime Minister, Robert Peel).

Violence from this Chartist movement erupts in the city of Birmingham. Egremont himself appeals to Parliament. When Sibyl reads a particularly moving speech of Egremont's, advocating for the rights of the working class, she becomes impressed and enraptured by him. Shortly thereafter, Stephen Morley forces Sibyl (whose father has not returned from a protest meeting) to marry him. The two are both arrested, but Egremont rescues Sibyl and Morley rescues Sibyl's imprisoned father, Gerard.

After a period of imprisonment, strikes are organized across the country, some peaceful, some antagonistic and violent. Sibyl is taken hostage by one such group (the Hell-cats). There is a standoff between Egremont's group of men and his brother, Lord Marley's men. Marley, Morley, and Gerard all eventually die from this altercation.

As a result, Egremont becomes Lord of Marney in his brother's stead and Sibyl inherits an estate of her own. The two resolve to not give up the fight to unify England as one nation.