The novel is set in a fishing village in Dorset during the mid 18th century. The story concerns a 15 year old orphan boy, John Trenchard, who becomes friends with an older man who turns out to be the leader of a gang of smugglers.
One night John chances on the smugglers' store in the crypt beneath the church. He explores but hides behind a coffin when he hears voices. He finds a locket which contains a parchment, in the coffin belonging to Colonel Mohune. Unfortunately after the visitors leave, he finds himself trapped inside, and is only rescued two days later when two of the smugglers, Ratsey, the sexton and Elzevir Block, the innkeeper of the Why Not?, the local pub, investigate his disappearance. His aunt insists he leaves her house and Elzevir Block takes him in to live at the pub. (http://en.wikipedia.org/wiki/Moonfleet )