Spy Smasher (1942) is a Republic movie serial based on the Fawcett Comics character Spy Smasher, which is now the property of DC Comics. It was the 25th of the 66 serials produced by Republic. The serial was directed by William Witney with Kane Richmond and Marguerite Chapman as the leads. This serial was Chapman's big break into a career in movies and television. Spy Smasher is a very highly regarded serial. In 1966, a television movie was made from the serial footage under the title Spysmasher Returns.

Spy Smasher is a costumed American acting independently of the United States while it remains out of World War II. After discovering information about Nazi activities in occupied France he is captured and executed. However this is faked and he escapes back to the United States, meeting with his twin brother Jack (as Jack is incorrectly "recognized" and attacked by a Nazi agent) and Jack's fiance. The Nazi agent in America is The Mask, operating from a U-Boat near the coast. The Mask's attacks on America 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 planes, 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. However, Spy Smasher's brother Jack Armstrong was also killed by the Nazis earlier in the serial.

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This film, produced on 4 April 1942, fell into the public domain on 1 January 1971.