Moonlight is about a young lady called Henrietta. She lives on Dartmoor in the early 19th century. She lives with Mrs. Branwell, a distant relation because her mother has passed away and her father disappeared before she was even born. Mrs. Branwell is trying to make Henrietta into a proper young lady, but Henrietta is much happier running wild on the moor with the local highwaymen. She believes that the highwaymen think she's a boy called Harry. She is t interest in having pretty dresses and finding a good husband. She is having far too much fun galloping about like a wild thing. But her whole life is about to change. Her father has cast a long shadow. From the exotic island of Jamaica comes a messenger who will turn her life upside down. Matthew de Clifford is a Frenchman, but he is also condemned. He forms the most valuable part of her father's estate. He wants to buy his freedom, but he is so proud that she is convinced he is spy. When news comes that Napoleon has escaped from Elba, she is even more suspicious and turns to her hero, Blackjack, the highwayman who is the scourge of Dartmoor. Hunted by the magistrates' men, she must keep her identity a secret, keep her aunt safe, and somehow unravel the mystery that surrounds her father and the Frenchman.