Margaret Lockwood (Iris Matilda Henderson)
Michael Redgrave (Gilbert Redman)
Dame May Whitty (Miss Froy)
Paul Lucas (Dr. Hartz)
Basil Radford (Charters)
Naunton Wayne (Caldicott)
Cecil Parker (Eric Todhunter)
Linden Travers (Mrs. Margaret Todhunter)
Mary Clare (Baroness Isabel Nisatona)
Emile Boreo (Boris the Hotel Manager)
Googie Withers (Blanche)
Sally Stewart (Julie)
Philip Leaver (Signor Doppo)
Zelma Vas Dias (Signora Doppo)
Catherine Lacey (The Nun)

Intrigue, espionage and the effects on the lives and futures of passengers aboard a Trans-Continental Express emerge when a girl traveller returning from a holiday strikes up an acquaintance with a middle-aged English governess.

During the journey she mysteriously disappears from her compartment. The girl, seeking an explanation for the disappearance, is accused of hallucinating and is nearly convinced that her new friend does not exist. However, further enquiries made among the passengers reveal the curious behaviour of a group of foreign government agents who are also travelling as passengers.

Hitchcock was actually second choice as director. The production was ready to roll as Lost Lady, directed by Roy William Neill, with Charters and Caldicott already in place, when Neill became unavailable and Hitchcock stepped in.