Marlene Dietrich demanded to be costumed exclusively by fashion design house Dior. Dior demanded a screen credit and Paramount demanded and received a 25% discount.

Miles Malleson was also working on Golden Salamander at the same time.

Alfie Bass 's character is called The Electrician in production papers and on Bass's contract.

Alfred Hitchcock originally wanted to cast Tallulah Bankhead for the role of Charlotte Inwood. But the studio suggested casting Marlene Dietrich instead.

First cinema film of Lionel Jeffries.

In "Hollywood Babble On" 'Marlene Dietrech' is quoted as saying, "I did one film for 'Alfred Hitchcock' (I). Jane Wyman was in it. I heard she'd only wanted to do it if she were billed above me, and she got her wish. Hitchcock didn't think much of her. She looks too much like a victim to play a heroine, and God knows she couldn't play a woman of mystery - that was MY part. Miss Wyman looks like a mystery nobody has bothered to solve."

It was Playwright James Bridie who suggested that Alfred Hitchcock cast Alastair Sim. James Bridie also contributed additional dialogue on the script of this film.

Most of Irene Handl 's performance as Miss Mason, the maid, was removed in post production editing.

The scenes where Jane Wyman first enters Marlene Dietrich's home undercover she introduces her self as Doris Tynsdale, but Dietrich refers to her first as Phyliss, then Elsie, then Doris, then lastly Mavis. It was classic dialogue play for Hitchcock.

This movie is significant because it broke a long-established cinematic convention that flashbacks were always a true account of earlier events. In this film, though, the opening flashback turns out to be a lie, a device which at first baffled then enraged cinemagoers who felt that they had in some way been cheated.

Alfred Hitchcock:  turning to look at Eve in her disguise as Charlotte's maid.