Sherlock Holmes
Dr. John H. Watson (as H. Marion Crawford)
Inspector Lestrade
Doreen Meredith
Sgt. Wilkins (as Kenneth Richards)
Boris Turgoff (as O'Brady)
Henry Travers (as David Gedeon Thomson)
Heckler (uncredited)
Counter-protestor (uncredited)
Agatha Axton (uncredited)