had a natural son by an obscure woman named Lucy Walters.

This boy had been created Duke of Monmouth.

He was put forward by the designing Earl of Shaftesbury as the head of a faction, and as a rival to the Duke of York.
To ruin the Duke was their first object; and this they attempted by inflaming the people against his religion, which was Roman Catholic.

If they could thus have him and his heirs put out of the succession to the throne, Monmouth might be named heir apparent; and Shaftesbury hoped to be the power behind the throne.
Monmouth was weak, handsome, and vain, and was in truth a puppet in wicked hands; he was engaged in the Rye-house plot, and schemed not only against his uncle, but against the person of his father himself.

To satirize and expose these plots and plotters, Dryden (at the instance of the king, it is said,) wrote _Absalom and Achitophel_, in which are introduced, under Scripture names, many of the principal political characters of the day, from the king down to Titus Oates.