Nineteen-year-old returning champion Sean Kendrick competes against Puck Connolly, the first girl ever to ride in the annual Scorpio Races, both trying to keep hold of their dangerous water horses long enough to make it to the finish line.
Ten-year-old Leo's future and the fate of the extraordinary Whippet Hotel, where his father is the maintenance man, are at stake when a series of cryptic boxes leads Leo to hidden floors, strange puzzles, and unexpected alliances.