The Lady Vanishes

Iris Henderson, returning from Bandrika to marry, is stranded when a mountain avalanche blocks the railway. The group of passengers must spend the night at a nearby hotel while a number of curious travelers gather. Among them are Charters and Caldicott, cricket enthusiasts, and Miss Froy, a governess and music teacher.

That evening Iris is disturbed by a loud clarinet coming from the room above hers. Gilbert Redman, an ethnomusicologist, is playing for local folk dancers and refuses to be quiet when Iris complains. She fails to have him moved after he confronts her.

The next morning at the railway station Miss Froy drops her glasses near Iris and the others. Iris tries to return Miss Froy's glasses, but a large planter falls from above and strikes her on the head. Miss Froy helps Iris onto the train and waves goodbye as Iris faints.

Iris finds herself in a compartment with Miss Froy and several other passengers. Also aboard are Charters and Caldicott, Gilbert Redman, Dr. Todhunter and his mistress posing as Mrs Todhunter, and a brain surgeon named Dr. Hartz who claims Iris may be suffering concussion. Gilbert agrees to help search for Miss Froy.

Iris joins Miss Froy in the dining car for tea, and Miss Froy seems to entrust her with a package of tea. After they return to the compartment, Iris falls asleep and wakes to find Miss Froy missing. Most passengers and staff deny ever seeing her, and Todhunter pretends not to remember Miss Froy to protect his affair.

Dr Hartz suggests Iris may be suffering from concussion-related hallucinations, and Charters and Caldicott fear they will miss their cricket match, so they claim not to remember Miss Froy. Todhunter's mistress confirms seeing Miss Froy, deepening Iris's doubt unless Gilbert helps investigate. Gilbert agrees to assist Iris in the search.

At the first stop, a patient with head bandages is brought aboard alongside a seemingly deaf-mute nun. A woman dressed exactly like Miss Froy, Madame Kummer, appears and claims to have helped Iris. Iris begins to doubt her memory, but Gilbert's clues convince her that Miss Froy exists.

Iris recalls having tea with Miss Froy and sees where she wrote her name on a window. Gilbert notices a tea-package wrapper sticking to a corridor window, matching Miss Froy's brand. These clues strengthen Iris's belief that Miss Froy is real and not a hallucination.

Iris and Gilbert locate Miss Froy's glasses in the baggage car, but their search is interrupted when magician Signor Doppo attacks, causing a struggle during which they lose the glasses. Doppo escapes, leaving Iris and Gilbert more determined to uncover the truth.

Dr Hartz reveals that Miss Froy is the patient and that he is part of a conspiracy to abduct her. The false nun is uncovered as a British operative, but loyalty to Britain prevents her from drugging Iris's group. Iris and Gilbert escape and swap Miss Froy back into the train with Madame Kummer.

As the train nears the border, Hartz discovers the plan and diverts the engine onto a branch line where soldiers lie in wait. Gilbert and Iris alert the other passengers and organize resistance, and they manage to subdue a soldier to seize his pistol.

A gunfight erupts when Miss Froy reveals she must escape because she is a British spy. Todhunter is shot dead while attempting to surrender, and the false nun is wounded while trying to switch tracks. Gilbert and Caldicott pull the disguised woman back onto the train as the situation unfolds.

In London, Charters and Caldicott discover the Test Match has been cancelled due to flooding. Iris and Gilbert hurry to the Foreign Office, where Miss Froy's message is finally revealed when she plays the tune on the piano, signaling her mission's success.