The Swallows and Amazons are in
Lowestoft, preparing for a cruise aboard a
schooner, the
Wild Cat, with
Captain Flint, the Blacketts' uncle Jim Turner. Unfortunately the other adult (Sam Bideford) cannot come and so the cruise is threatened until Peter Duck, an elderly
seaman, offers to come along to help. In the harbour a larger black schooner, the
Viper, is fitting out for a voyage and Peter Duck's presence aboard the
Wild Cat interests Black Jake, the
Viper’s captain. Peter Duck spins a yarn about a treasure that he saw being buried long ago, when
marooned on a desert island in the
Caribbean Sea, and which Black Jake wants to find. When the
Wild Cat sails, the
Viper is quick to follow and trails her down the
English Channel, at one point threatening to board her in the night. In a fog off
Land's End, the crew of the
Wild Cat give the
Viper the slip but pick up the
Viper’s
cabin boy, Bill, who has been set adrift to try and fool the
Wild Cat’s crew with false signals. They continue across the
Atlantic Ocean to Crab Island where they spend several days searching in vain for Peter Duck's treasure. When a
hurricane blows up, Peter Duck and Captain Flint take the
Wild Cat out to sea to ride out the storm, leaving the Swallows and Amazons ashore. There is an earthquake during the storm, and when the schooner returns all the paths to the treasure-hunters' camp are blocked by landslides and fallen trees. However, a fallen palm tree exposes a small box, Peter Duck's treasure, which the children recover. They decide to sail round to the anchorage as the land route is blocked. While Captain Flint attempts to cross the island to rescue the Swallows and Amazons, the
Viper arrives and Peter Duck and Bill are captured. The crew of the
Viper also go ashore to look for the treasure. The children rescue Peter Duck and Bill, and then the
Wild Cat sails back to the other side and they pick up Captain Flint just before Black Jake arrives. They attempt to sail away from the island but the wind dies and the
Viper looks like catching them, but they are saved by a
waterspout which destroys the
Viper. They return home safely without further incident. The contents of the treasure chest proves to be a collection of nautical literature and a sizeable number of
pearls, which --- though indeed of considerable value --- turn out to not really be worth the vast fortune that one might have expected in a buccaneer's buried chest. The story's main characters divide up the assets appropriately, with funds going to sensible and practical ventures. ==References==