The Duke's Ballad is the tale of Aisling, a young witch from a family gifted with a magical power that she must protect from her brother, Kirion, who wields magic unlike the rest of the family's. He gains power only by a terrible means: by killing others who wield magic.

Years ago, Aisling fled her native Kars when Kirion, working for the Duke of Kars, tried to kill her. Since Aisling's departure, Kirion has tightened his insidious hold on Duke Shastro. The malevolent sorcerer's dark influence works through Shastro to cast a deadly pall over all of Kars. A fatal chain of events is triggered when Kirion pitches the people of Kars into a war with a neighboring clan.

Aisling recruits her younger brother Keelan and returns in disguise, determined to undermine Kirion's power and unseat his evil pawn from the throne. Accompanied also by a catlike telepathic beast, Aisling becomes part of Shastro's court. But even as she begins to learn the ways of court power, a brutally cold winter besieges the land, testing the endurance of the people of Kars, who have little cheer in that darkest season.

As Kars and its people contend with Kirion's depredations, the warring clan's raids, and the devastating winter, Aisling and Keelan must somehow, through guile, persistence and ingenuity, find a way to avoid the attention of their dangerous older brother, and save the people from his murderous sorcery. Only if they can survive Kirion's terrible power can they deliver the dukedom into the peace and prosperity it once knew.