This was the first in Universal's 11-film series featuring Basil Rathbone and Nigel Bruce as the slender sleuth and his rotund sidekick, though the two actors had already played the roles in two films for 20th Century-Fox. The wartime plot is simplistic, with Holmes searching for a traitor in the government - did Churchill know? - supplying a Nazi broadcaster with news of sabotage and disaster. It's not the best of the series, with the informer as obvious as the Union flag that's raised so laboriously in Holmes's patriotic speeches.

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.