A mysterious coded message. A search for a fabled perpetual motion machine. A horse ride from hell. And a night in the exclusive Billionaire's Club House of Puzzles. If Gerald thought his term in a Scottish Highlands school camp was going to be all snow-covered heather and tartan rugs he couldn't have been more wrong. With Professor McElderry in the clutches of Gerald's nemesis Sir Mason Green and a seemingly impossible task required to save his life, the stakes are high and the heat is on. In The House of Puzzles, the fifth book of the Billionaire Series, Gerald, Ruby Sam and Felicity face their greatest challenge yet.