Jack Armstrong and Admiral Corby help Alan fight what Nazi Agent?
Alan Armstrong as the Spy Smasher is a costumed vigilante and freelance agent, not associated with the US government as the country has not yet joined its allies in World War II.  After discovering information about Nazi activities in occupied France, he is captured and ordered to be executed.  However, with the help of Pierre Durand, he escapes back to the United States, meeting with his twin brother Jack. Jack is incorrectly recognized and attacked killed by Nazi agent on American soil codenamed The Mask. Eve Corby plays Jack's fiancé. The Mask, operates from a U-Boat near the coast.
The Mask's attacks on the United States begin with an attempt to flood the country with forged money and destroy the economy.  When this is defeated, he continues with other attacks including destroying aircraft, oil and munitions intended for Britain.  Constant defeats at the hands of Spy Smasher, with support from Jack Armstrong and Admiral Corby, also leads the villain to take the fight back to the masked hero. In the end, the villain is killed aboard his own U-Boat in a sea of flaming oil.
The Mask