Before the surgery, the members of the Black Dragon Society are played by six Chinese actors. After the surgery, they are played by the same six gentlemen who play the six businessmen later (i.e., earlier in the film). One of the Chinese actors is Keye Luke, in a bit role. He is the man on whose face Bela Lugosi's character is seen operating.
Filming began January 22 1942, one of Hollywood's earliest replies to the Japanese attack on Pearl Harbor a month earlier. This was the 3rd of Bela Lugosi's 9 Monogram features.
This is Bela Lugosi's only spy movie. At the time, he was addicted to morphine and suffering from very bad arthritis, and had to work to keep the money rolling in.