The chapter-crunched version of this 196 minutes, 12-episode serial from Republic finds Canada being bombed mercilessly by a mysterious-enemy plane (shaped like a boomerang) called the Falcon, under the supervision of Admiral Yamata, Count Baroni and Marshal von Horst, chiefs of the Axis Fifth Column in Canada. No one can identify the plane until American inventor, Professor Marshall Brent, and his daughter Carol arrive with a new type of airplane detector. This poses a threat to the Axis chiefs in preparing western Canada for an invasion and they have him kidnapped by local Quisling Gil Harper. RCMP Sergeant Tom King attempts to rescue Brent, but the inventor is killed when a plane in which he is held captive crashes into a riverboat.