England, at the start of World War Two. Mysterious wireless broadcasts, apparently from Nazi Germany are heard over the BBC. They warn of acts of terror in England, just before they take place. Baffled, the Defense Committee call in Sherlock Holmes.
| Actor | Role |
|---|---|
 Basil RathboneSherlock Holmes | Sherlock Holmes |
 Nigel BruceDoctor Watson | Doctor Watson |
 Evelyn AnkersKitty | Kitty |
 Reginald DennySir Evan Barham | Sir Evan Barham |
 Thomas GomezR.F. Meade | R.F. Meade |
 Henry DaniellSir Anthony Lloyd | Sir Anthony Lloyd |
 Montagu LoveGeneral Jerome Lawford | General Jerome Lawford |
 Olaf HyttenAdmiral Sir John Fabian Prentiss | Admiral Sir John Fabian Prentiss |
 Leyland HodgsonCaptain Roland Shore | Captain Roland Shore |
 Mary GordonMrs. Hudson | Mrs. Hudson |
 Hillary BrookeJill Grandis | Jill Grandis |
 Harry CordingCamberwell | Camberwell |
 Herbert EvansSmithson - Barham's Butler (uncredited) | Smithson - Barham's Butler (uncredited) |
 Fred GrahamMeade's Henchman (uncredited) | Meade's Henchman (uncredited) |
 Gavin MuirBBC Radio Announcer (voice) (uncredited) | BBC Radio Announcer (voice) (uncredited) |
 Edgar BarrierVoice of Terror (voice) (uncredited) | Voice of Terror (voice) (uncredited) |
| BBobby HaleBar Patron (uncredited) | Bar Patron (uncredited) |