 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 (Abner Biberman), Count Baroni (Nestor Pavia) and Marshal von Horst (Wilheim/William von Brincken using his WW II alias of William Vaughn), chiefs of the Axis Fifth Column in Canada. No one can identify the plane until American inventor, Professor Marshall Brent (George Irving), and his daughter Carol (Peggy Drake) 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 (Douglass Dumbrille.) RCMP Sergeant Tom King (Allan Lane) attempts to rescue Brent, but the inventor is killed when a plane in which he is held captive crashes into a riverboat. Carol, determined to carry on her father s work and with King s aid, manages to prevent the enemy agents from capturing the detector, and destroys the device (many chapters later) when the agents make a last desperate attack on the cabin where it is hidden. She is captured and taken to the crater of a volcano, where the ring makes its headquarters.