Returning home from the Balkans in the 1930s Iris Carr boards a train with fellow Brits the elderly Floodporter sisters,brusque vicar Barnes and his fretful wife and a reticent couple who are plainly having an affair. After a blow on the head Iris is befriended by brisk Miss Froy,former governess to a family headed by a chilly baroness travelling with her poorly sister and medical staff. When Miss Froy disappears everybody denies ever seeing her,claiming Iris is hallucinating after the knock to the head. Only language student Max Hare is sympathetic and even he has his doubts when a German woman is produced and passed off as the missing lady. Max even unwittingly becomes part of the plot to dissuade Iris from her search for the truth but is eventually swayed by her persistence and helps her solve the mystery of her friend's disappearance...