Scottish orphan David Balfour is betrayed by his wicked uncle Ebeneezer, who arranges for David to be kidnapped and sold into slavery so that he cannot claim his inheritance. The boy is rescued and befriended by Alan Breck, a Scottish rebel fighting on behalf of his country's independence from the British.

On holiday with their mother in the Lake District in 1929 four children are allowed to sail over to the nearby island in their boat Swallow and set up camp for a few days. They soon realise this has been the territory of two other girls who sail the Amazon, and the scene is set for serious rivalry.