Crane operator Peter Thompson (Redgrave) is travelling to work on a train when he happens to see a man stabbing a woman through the window of an apartment. He frantically disembarks and leads a police constable into the apartment, only to find that it was a down-on-his-luck illusionist, Zoltini (Lukas), and his assistant-wife, Vivian (Gray), rehearsing a stunt. The publicity that this brings to the incident gives Zoltini a chance to relaunch his career. However, Zoltini's insane possessiveness about Vivian causes him to suspect that she is having an affair with Thompson, and when Vivian runs away with Thompson's assistance in the middle of Zoltini's comeback performance, he won't let her go so easily...
- Bookends: The main action begins with Thompson witnessing through the train window what he thinks is Zoltini stabbing his wife. The last scene shows Thompson travelling on the same train the next day, looking at Zoltini's apartment window, and feeling relieved that all is normal within...except that this time, Zoltini has in fact shot his wife dead, but her body can't be seen from the passing train as she is slumped on the floor.
- Crazy Jealous Guy: Zoltini can't bear his wife so much as smiling at another man, and pushes away one of his performers for merely giving her an innocent, friendly hug.
- Damsel in Distress: The whole plot is driven forward by Thompson's desire to help Vivian, whether it is by saving her from being "murdered" or by acting as her getaway when she makes up her mind to leave Zoltini. Fittingly, the US release was titled Lady in Distress.
- Downer Ending: Almost immediately their reconciliation, Zoltini finds the contract that Vivian had signed with Preston's company after walking out from the show - a contract which she no longer intended to keep - and in a fit of jealous rage, shoots Vivian dead. Ironically, Thompson's train happens to travel past the apartment at the same time, just like the day before, but because Vivian is slumped on the floor, he can't see or try to save her this time.
- Heroic BSoD: Thompson goes into one after his fight with Zoltini sends the latter tumbling down into the river to his apparent death. He gets better when he hears that Zoltini was rescued.
- Imagined Innuendo: The reporter who is taking down Thompson's story about the "stabbing" initially gets the wrong idea about the kind of incident Thompson is describing:Thompson: I was looking out of the window on the underground, travelling overground,...when I saw a man messing about with a girl.Reporter: What?!Thompson: He was trying to stick a knife into her.Reporter: Ha, knife, I get you.
- Old Flame: Preston's feelings for Vivian clearly go beyond being Just Friends, although on Vivian's part, it is more of a case of Old Flame Fizzle, as she really does love Zoltini.
- Sexless Marriage: It is strongly implied that the Thompsons' marriage has come to this state, not because they don't love each other, but because one has to work during daytime while the other has to go on a night-shift. This might explain why Thompson falls head-over-heels for Vivian.
- Trailers Always Spoil: The trailer for this film outright shows Zoltini shooting his wife.
- Working-Class Hero: Thompson, although he is the cheerful rather than the bitter variety.
- Your Cheating Heart: Thompson is already married to Pat but that doesn't stop him from developing a crush on Vivian. Right after she walks out on Zoltini, he kisses her and promises to stand by her no matter what.