The hook of the story is that, in a reversal of the common serial "Masked Mystery Villain" stock character, the audience doesn't know who the hero is until the final reel—all the audience is told is that The Masked Marvel is one of a group of special investigators (the same plotline is used in the Republic serial The Lone Ranger).

[1] In terms of cost per chapter, this was Republic's third most expensive serial, behind Radar Men from the Moon and The Tiger Woman.

Despite this, Tom Steele was given no screen credit at all, even for the bit parts and stunts he performed in addition to the title role.

Just two weeks after the production of the serial had been completed, Bacon was murdered and died moments after exiting his car.

Instead, Sakima, sitting behind his desk in his secret basement, simply (although incorrectly) announces "So, Jim Arnold is the Masked Marvel".

[2] In addition to playing the main character, Tom Steele was also the stunt gaffer on this serial.

[2] As an odd outcome of playing both the Masked Marvel and other stunts and bit parts, in one scene Tom Steele chased himself up some stairs.

[2] Steele himself was doubled by a dummy in the scene in which the Marvel is thrown off the top of an enormous gas tank.

[1] The Masked Marvel was one of twenty-six Republic serials re-edited into features for television release in 1966.