Hello, Gerald. I hope this isn't too weird for you—a letter from beyond the grave! By now you are my heir and worth a good deal of money. I hope you don't mind. . . . I expect you've figured out that I was murdered. I would like you to find out who did it.

Gerald Wilkins had only been hoping for a ski holiday, but plans change when a great aunt he's never met leaves him her entire estate worth twenty billion pounds! Whisked by his parents to London, England, Gerald is given a letter and told not to open it until after the funeral.

Now he's got a mystery to solve. With the help of his new friends, Sam and Ruby Valentine, Gerald follows the clues into secret passageways, a musty jumbled bookshop, an ancient crypt and a colossal cavern where the secret of a priceless treasure lies protected by deadly booby traps.