Jock McLock's Piratical Adventure — Elizabeth Klein

This story can be summed up as a boy's adventure in all its quirky day-dreaminess and fascination with spies, flamboyant villains who own islands and wear white suits and a mutinous, but very dead pirate. When half of a treasure map ends up in a box of books at the local fete, Jock McLock decides to visit the donator. He's heard plenty of strange tales about her from the kids at school, but it's nothing like meeting Mrs Trelawney in the flesh. It's all connected to his mother winning a holiday to the Bahamas, which turns out to be full of perils for poor Jock, a wild treasure hunt with gunmen bent on finding the pirate's treasure before Jock does.