A castle in the clouds

The Castle in the Clouds is a hotel on top of a Swiss mountain. Its glory days may be behind it, but every year for New Year's the staff never fails to celebrate the great dance, returning the hotel to its former splendor. Seventeen-year-old Fanny, one of the hotel's staff, is working to keep the guests happy and comfortable when she discovers something off about some of the guests--they are not who they are pretending to be. There is a Russian woman who claims to possess a diamond worth millions of dollars, and a boy named Tristan, who is attractive, sure, but who prefers to climb the outer face of the hotel instead of its stairs. Fanny, putting her job at risk, goes to investigate.