Martin Watts, a bookseller, is captured by Royalists. Jane Afton's brother Nat is taken too. They suffer inhumane treatment as prisoners-of-war.

In Oxford Castle jailor William Smith tortures, beats, starves and deprives his helpless victims. Can Jane rescue her sick brother before he dies of neglect? Will Martin dare to escape? Based on real events in the English Civil War, Lindsey Davis retells the grim tale of Captain Smith's abuse of power in Oxford prison - where many died in misery though a lucky few survived.