Charlie had his chocolate factory. Stanley Yelnats had his holes. Leo has the wacky, amazing Whippet Hotel. The Whippet Hotel is a strange place full of strange and mysterious people. Each floor has its own quirks and secrets. Ten-year-old Leo Fillmore should know most of them; he is the maintenance man's son, after all. But a whole lot more mystery gets thrown his way when a series of cryptic boxes are left for him...boxes that lead him to hidden floors, strange puzzles, and unexpected alliances. Leo had better be quick on his feet, because the fate of the building he loves is at stake...and so is Leo's own future!