In 1757 the villagers of Moonfleet, led by innkeeper Elzevir Block engage in smuggling. The cruel magistrate Mohune ambushes the gang, killing Elzevir's son Davey and subsequently Elzevir takes in young orphan John Trenchard, who is conducting a secret friendship with Mohune's daughter Grace. Another ambush of the smugglers leads to Mohune being shot and Elzevir and John go on the run, taking the document that they hope will lead them to discover Blackbeard's hidden diamond. They eventually locate it but are caught and sentenced to be slaves in the Indies. However their ship runs aground near to Moonfleet and they swim ashore though only one will live to tell the tale.