Gerald’s murdered great-aunt has left him her entire fortune of £20 billion, and an envelope full of clues. Instead of enjoying a trip to the snow in Australia, thirteen-year-old Gerald finds himself heading to London on a private jet with his parents to attend her funeral. Meanwhile, the world’s most valuable diamond has been stolen, rather comically, from the British Museum, and no one can figure out how. With the help of two new friends, Sam and Ruby, Gerald must solve this double whodunit.