A stunning new adaptation of the classic 1930s thriller that sees a beautiful, spoilt young woman risking her life to solve the mysterious disappearance of her travelling companion. Iris Carr (Tuppence Middleton) is travelling across Europe by train when she unwittingly becomes embroiled in a sinister Balkan plot. Feeling disorientated after a fall, Iris is befriended by Miss Froy (Selina Cadell), an elderly English woman sharing her carriage. But when she wakes up from a few hours' sleep, Miss Froy has vanished without trace. As fellow passengers claim the lady never existed, Iris faces danger and intrigue as she fights to discover the fate of Miss Froy - and prove that she's not going mad.