The Curious Cousins and the Smugglers of Bligh Island — Alex R. Carver

Nobody believes them. For Edward and Elizabeth, a summer on Bligh Island with their cousin Henrietta (it's Henri!) is like being sentenced to die of boredom. But adventure awaits! The island harbours family history and the hideout of a band of 18th century smugglers. It's all great fun . . . until modern-day smugglers show up! The kids take the case to the police, but the local officer won't believe them. They're on their own, and their lives are in danger. How can they stop the smugglers?