Returning home from the Balkans during the 1930s, Iris Carr boards a train. After a blow to the head Iris, is befriended by a Miss Froy - former governess to a family headed by a baroness travelling with her poorly sister and medical staff. When Miss Froy disappears everybody denies ever seeing her,claiming Iris mustve imagined Miss Froy, after the knock to the head. Only language student Max Hare is sympathetic and even he has doubts. When a German woman is produced and passed off as the missing lady, Max unwittingly becomes part of the plot to dissuade Iris from her search for the truth.