Apothecary John Rawlings has been summoned to Devon by Elizabeth di Lorenzi, his beautiful but unpredictable mistress. Leaving his young daughter Rose in the good care of her grand-father Sir Gabriel Kent, Rawlings sets off for Exeter on board the stagecoach. His fellow-passengers are a motley crew, and include a large and talkative German lady; Cuthbert Simms, a dance-master; and Jack Beef, the so-called 'Black Pyramid', a bare-knuckle fighter. Before the journey's end a man has been found brutally murdered at the Half Moon Inn, and Rawlings is once again drawn, somewhat reluctantly, into a complex and dangerous intrigue.