The film combines elements of Doyle's short story "His Last Bow", to which it is credited as an adaptation, and the real-life activities of Lord Haw-Haw.

Holmes is called into the "Inner Council" of British Intelligence by Sir Evan Barham (Reginald Denny), to assist in stopping Nazi saboteurs operating in Britain, whose activities are announced in advance in radio broadcasts by "The Voice of Terror".

Later, Holmes and Watson go to the Limehouse district of London, where they meet with Gavin's wife Kitty (Evelyn Ankers).

Using a tip from Kitty, Holmes and Watson go to the old Christopher Docks, where they are followed by Sir Anthony Lloyd (Henry Daniell) of the council.

With the support of British troopers, Holmes captures Meade and a group of German soldiers stationed in an abandoned church.

[6] Shortly after this, Warner Bros. displayed an interest in adapting "The Speckled Band" with Rathbone and Bruce as Sherlock Holmes and Dr. Watson respectively.

[6] This film was not made per a notice in the Hollywood Reporter claiming there were "difficulties encountered in clearing all rights in the complicated copyright setup covering Holmes yarns.

"[7] Winsten commented on the film's contemporary setting, concluding that "It is to be feared that neither the Holmes series nor the war effort are greatly aided by this ambitious but uneffective attempt to merge the two.