Elwood Henderson invents the Orotron, a large device which can extract various minerals and elements in their minute quantities from sea water. Nazi agents (the serial, released in 1945, is set in 1938) plan to use the Orotron in order to obtain enough gold to buy up key American industries for their own use and purpose. Henderson is also taken prisoner by the Nazis, since he has to manufacture the gas tubes in order to make the Orotron work, when the present ones wear out. Government agent Tom Brant, police detective Jack Ryan, and reporter Janet Lowe, team up to find Henderson and round up the agents responsible for his and the Orotron's disappearance, including the Master Key, the unknown head agent of the Nazis in the US. Very good script overcome some of the weak fights in the serial. Many of the cliffhangers are so-so, and at times just look like the writers put them in there from making the chapters run a reel extra. Stone, Moore, & Wiley are all believable as Brant, Ryan, and Lowe respectively. Addison is very villainous Donohue, second Nazi in command. LaRue is as good as he every would be as the leader of Lowe's teenage reporter friends, but Fougler has one of his better roles as Henderson. Great ending to the serial, one of the few that respects the intelligence of the viewer. Rating, based on serials, 8.