Adopted into a family of notorious Cornish smugglers, Pip of Pengersick takes to life on the high seas as she learns the trade of those who sail by a dark moon. Business is going well when a well-dressed stranger sends Pip, a small dog, and her friend, the smuggler Harry Carter, on an urgent mission to London - ordered by the King of England himself. A secret mission takes the intrepid Pip and Harry to France, a country in the grip of revolution. Pip's Cornish home seems a long way away - will Pip and Harry ever make it back alive without the shadowy figures who seem to dog their every footstep...