Michael Armstrong (Newman) is an esteemed American physicist and rocket scientist. He is supposed to attend a scientific conference in Copenhagen, but instead heads for East Berlin. Apparently defecting to East Germany. He is soon followed by Sarah Sherman (Andrews), his assistant and fiancée. She is very reluctant in doing so but remains loyal to him.
The defection is actually a ruse. Armstrong wants to meet Gustav Lindt (Ludwig Donath), the chief scientist in the East German military, to establish the extent of the Eastern Bloc's knowledge on anti-missile systems. He supposedly has a way to exit the country at will. Stasi, the East German state security service, has a very different view on the matter. Armstrong and Sherman are about to find out that entering East Germany was easy. Leaving East Germany is another matter entirely.
Generally viewed as a letdown after Hitchcock's remarkable decade-and-a-half run, faulted for an unengaging script and a lack of chemistry between Newman and Andrews (one writer observed that in their scenes together they seem like they're characters from two entirely different films). But it's still intriguing as Hitchcock's reaction to the James Bond series (which borrowed a lot of its style from North by Northwest), and for its colorful European setting and characters.
- Alliterative Name: Sarah Sherman.
- Anti-Villain: Karl Manfred, Michael's East German contact, holds Armstrong in high regard as a scientist and doesn't seem totally happy to be aiding the Stasi as they keep tabs on Michael.
- Badass Longcoat: Gromek's leather overcoat.
- Bavarian Fire Drill: Michael shouts "Fire!" in a crowded theatre as a distraction to escape from the East German police.
- Break Her Heart to Save Her: Michael does this to Sarah (in a way) to keep his secrets from her at the beginning of the film.
- Captain Obvious: Upon being told that Michael is going to East Berlin, Sarah points out "But—that's behind the Iron Curtain!" Even the film's writers hated that line but Hitchcock refused to change it, probably because it functions as a semi-Title Drop.
- City of Spies: East Berlin; not just the Stasi but Deep Cover Agents working against the Commies.
- Cool Old Lady: Countess Kuchinska, a little eccentric but she sacrifices her own chance to get to America by helping the heroes get away.
- Creator Cameo: Hitchcock holding a baby on his knee in the lobby of the hotel in Copenhagen, while the score briefly plays the "Funeral March of a Marionette" riff.
- Eureka Moment: Lindt has one upon realizing he's been giving up his secrets while learning nothing from Armstrong in return.
- Fake Defector: Michael Armstrong uses defection to East Germany as a cover for helping America in the Cold War.
- Faux Affably Evil: Gromek tries to ingratiate himself to Armstrong by noting that he lived in New York for a while, and expresses fondness for American culture, but he's too Obviously Evil for it to really work.
- Graceful Loser: When Countess Kuchinska is unable to get away along with Michael and Sarah. She sadly notes her disappointment, but apparently doesn't blame the couple.
- Hidden in Plain Sight: Professor Lindt's anti-missile equations are on a chalk board for any and all to see. Makes sense since he was working at a (supposedly) secure facility were only authorized personnel would be allowed inside.
- Hot Scientist: With Paul Newman in the role, Armstrong is a male example. His big scene has him working out physics equations on a chalkboard.
- I Did What I Had to Do: Michael justifies his risky, reckless scheme by saying it will help America and ultimately help eliminate the nuclear threat, but he has to lie to his fiancée, then betray his East German hosts to accomplish it. Then he has to help cover up a killing.
- Ivy League for Everyone: Averted with Michael, who teaches at the University of Chicago and got his doctorate at Caltech.
- Jerkass: The Ballerina.
- MacGuffin: The Soviet Union's anti-missile system equations.
- Plot-Based Voice Cancellation: Michael revealing to Sarah that he's a Fake Defector is depicted via a distant Silence Is Golden long shot.
- Rasputinian Death: Hermann Gromek, the first Stasi agent Armstrong attempts to kill, takes a good long while to go down, including spending most of the climactic fight with a butcher knife sticking out of his chest. Hitchcock's main goal with the film was to show how hard it could really be to kill someone.
- Reality Ensues: It turns out that killing someone isn't as easy as it looks in the movies. This was a deliberate choice by Hitchcock because a number of spy thrillers at the time made killing look effortless.
- Reality Has No Subtitles: None of the spoken German is subtitled, but it's usually obvious what's being said.
- La Résistance: Pi, the underground anti-Communist network that Michael works with.
- Silk Hiding Steel: The seemingly-simple farmer's wife seems quite knowledgeable about how to kill people and hide bodies. Presumably she's also a Pi agent with an intelligence background.
- The Stool Pigeon: The driver of The Taxi who took Michael to the farmnote informs the Stasi about the whole incident when he sees a news story about Gromek's disappearance.