On a train headed for England are a mixed a group of travellers, one of which, young Iris, befriends a certain Miss Froy. Iris falls asleep after luncheon, and wakes to find her friend has disappeared. The other passengers ominously deny Miss Froy ever existed, so Iris begins to investigate with another traveller, and, as the pair try to find answers to the mysterious disappearance, romantic sparks fly.
The play is based on the original book, but aficionados of the 1938 Hitchcock film will find this play version just as gripping.