When the mysterious "Doctor Satan" (Edwardo Cianelli) attempts to takeover the United States with his army of mechanical men, idle playboy Bob Wayne (Robert Wilcox) dons his late father's copper mask to become a crusading vigilante. Originally intended to be a Superman serial, the characters were all subtly changed into the supporting cast for a new hero--the Copperhead. MYSTERIOUS DOCTOR SATAN is action-packed and full of the amazing stunt work of the ever-agile David Sharpe! (1940-Republic Pictures)