Margaret Lockwood

Passengers on a scheduled train out of the mountainous European country of Mandrika are delayed by a day due to an avalanche, and thus get up close and personal with each other out of necessity in the only and what becomes an overcrowded inn in the area. Once the train departs, the one person who it is uncertain is on the train is a middle aged English governess named Miss Froy (Dame May Whitty).

A young woman on a train, enroute back to England from Switzerland, meets a charming older lady who promptly disappears. The other passengers deny ever having seen her, leading the young woman into a complex web of mystery and high adventure.