Trivia

The opening sequence showing the Edinburgh Express preparing for departure uses very short clips from Rome Express (1932).

Alan Mowbray had previously appeared in two other Sherlock Holmes movies--Sherlock Holmes (1932) and A Study in Scarlet (1933). Alan Mowbray, who plays Maj. Duncan-Bleek, played Lestrade to Reginald Owen's Holmes in the 1933 production of A Study in Scarlet (1933).

One of several titles in the Sherlock Holmes series whose original copyrights were apparently not renewed and have thereby fallen into public domain; as a result, seriously inferior copies are presently being offered by a number of DVD dealers who do not have access to original studio masters. Terror by Night (1946) is one of four films films in the series which are in the public domain. Terror by Night (1946) is available for free download at the Internet Archive.

The film's plot is a mostly original story not directly based on any of Arthur Conan Doyle's Holmes tales, but it uses minor plot elements of "The Adventure of the Blue Carbuncle," "The Adventure of the Empty House," "The Disappearance of Lady Frances Carfax," and "The Sign of Four."

Lady Carstairs states the value of the diamond was £50,000. That amount equaled $201,600 at the time, which equates to over $2.8M in 2021.