Anna Bomasch (Lockwood) and her father, Axel, (James Harcourt) need to escape Czechoslovakia: Axel is the inventor and manufacturer of an armour-plating the Nazis will find very useful as they slowly roll into their annexation of the country. Axel escapes, but Anna isn't so lucky and is thrown into a concentration camp. Happily for her, she finds a friend among the prisoners, Karl Marsen (Henreid). They both escape to London, England, where Anna knows her father must be. She contacts him through songster and British agent, Gus Bennett a.k.a. Dickie Randall (Harrison). But it turns out that Karl is not what he seems: he was planted in the concentration camp to escape and have Anna lead him to her father.
And so, they are both tricked and forced to return to the Continent. Gus, in the meanwhile, feels responsible for their kidnapping, so he devises a covert plan to disguise himself as a Gestapo man to try to free Anna and her father from the Nazi grip and Karl's unflinching coldness.
See The Lady Vanishes for a similar setting of pre-war conditions and intrigue.
This film contains the following tropes:
- Artistic License History: Caldicott and Charters, two British citizens, traveling around freely on a German train after the September 3, 1939 declaration of war. This is not a thing that happened; enemy aliens in Germany were interned. (It happened to P. G. Wodehouse in Real Life after the Nazis overran France.)
- Beauty Is Never Tarnished: Even in a concentration camp, Anna's appearance suffers nothing except a little tousled hair.
- Bottomless Magazines: The climax is a shoot out between Karl's men and Randall. Unsurprisingly, their guns never run out of magazines. Although Randall's gun does eventually run out, it's after a very long battle with an extremely small gun.
- Cable-Car Action Sequence: The group have to cross into neutral Switzerland using cable cars. Randall has to commandeer it to get Anna, her father, and the Brits over, while he has to fight off the Nazis from coming in.
- Cannot Convey Sarcasm: Invoked. When Schwab says, "This is a fine country to live in!" he gets in trouble for treason. He weasels out by saying that he actually said, "This is a fine country to live in!" He is advised against making statements that could be construed two ways in the future.
- Comically Missing the Point: When a British man visiting Germany is informed that the news stand doesn't sell British magazines (Punch to be exact), he says, "Sold out, I suppose?"
- Continuity Nod: Caldicott and Charters, the two English goofs first seen in The Lady Vanishes, appear again, with the same actors playing the same characters.
- Dressing as the Enemy: Randall dresses in the black Gestapo uniform because it's part of his covert mission.
- Follow That Car: As soon as the ruse is found out, Karl and his men go after Randall and the gang.
- Herr Doktor: The man Karl receives his orders from is a Nazi optometrist living in the heart of London.
- High-Class Glass: Invoked. Randall wears a monocle when he disguises himself as a Nazi.
- Hostage MacGuffin: Axel, kidnapped by the Nazis so they can force him to make steel.
- I Have Many Names: Dick Randall has at least two aliases: the one we know of is Gus Bennett, the seller of dopey love songs by the British seaside.
- Impersonation Gambit: Randall has to pretend to be a Gestapo man in order to save Anna and her father. Since he's already a bit of snoot, he's able to pull off the haughty attitude of the Gestapo.
- Inadvertent Entrance Cue: Anna has met "Gus Bennett" at a seaside pier, but he has pleaded complete ignorance of her father. A frustrated Anna finally says "You don't know my father, you don't know anything about him, and you can't help me." Bennett then points at the water and says "Is that him?" Cue Anna's father on the boat.
- The Infiltration: Karl seems like he's part of La Résistance when he's in the concentration camp. All this playacting is really to fool Anna.
- Mugged for Disguise: The SS officers are rid of their uniforms by Charters and Caldicott in order to help Randall.
- Only a Flesh Wound: Of the "shot in the shoulder" variety. Possibly one of the most outrageous examples in history, as not only does Randall keep shooting with that same arm where he just took a bullet in the shoulder, he manages to hang one-handed from a cable car by that same arm.
- Out-of-Context Eavesdropping: Charters and Caldicott do this and, surprisingly, don't mess things up. Charters overhears Karl's telephone call where he finds out Randall isn't a Gestapo man and plans to ambush him when they get to Munich. Charters then assumes that Randall must be who Caldicott thinks he is (old Dickie Randall!) and they plan to make sure by sending a note to him.
- Reverse Mole: One of the guards in the camp helps them escape, but this is a subversion. The escape was planned.
- Gus Bennett/Dick Randall goes undercover as a German officer.
- Take That!: Gone with the Wind is shown being sold on a shelf right next to Mein Kampf. Also serves as a Historical In-Joke, because the book was very popular in Nazi Germany for all the wrong reasons.
- Translation Convention: Czechs and Germans all speak English to each other.
- "The Reason You Suck" Speech: In the camp, Karl gives one of these to some of the guards. This is later subverted by the fact that it was only done to make Anna trust him.
- Those Two Guys: Caldicott and Charters, who'd appeared in The Lady Vanishes a couple years earlier. They still love cricket. Actors Basil Radford and Naunton Wayne appeared in several films together, either explicitly as Caldicott and Charters or Expy versions.
- Those Wacky Nazis: They're so gullible!
- We Do Not Know Each Other: The type 2 variety: if Randall admits his association with Caldicott, his cover is blown, be shakes off Caldicott, but it's not enough to dispel suspicion from Karl.