The wheel spins

"Iris Carr's holiday in the mountains of a remote corner of Europe has come to an end, and since her friends left two days before, she faces the journey home alone. Stricken by sunstroke at the station, Iris catches the express train to Trieste by the skin of her teeth and finds a companion in Miss Froy, an affable English governess. But when Iris passes out and reawakens, Miss Froy is nowhere to be found. The other passengers deny any knowledge of her existence, and as the train speeds across Europe, Iris spirals deeper and deeper into a strange and dangerous conspiracy"--