Created by Bill Parker and C. C. Beck, Spy Smasher was introduced in Whiz Comics #2 and was the second most popular Fawcett Comics hero behind Captain Marvel. Alan Armstrong was a millonaire inventor who decided to use his intelligence to protect America during the war. By the 50s, there was no need for that, so he became Crime Smasher for one issue before disappearing until he made appearances in Crisis on Infinite Earths and The Power of Shazam after DC bought the characters of their former rival.

In the serial, both Alan and Jack Armstrong (both brothers are played by Kane Richmond) are on the wrong side of The Mask (Hans Schumm), including — spoiler warning — a chapter ending that does not end happily, as unlike every serial, one of them is killed.

While the twin idea was invented for the series, The Mask, Admiral Corby (Sam Flint) and his daughter Eve (Marguerite Chapman) are all directly from the comics.

In their book The Great Movie Serials: Their Sound and Fury Jim Harmon and Donald F. Glut claimed that this was ” the foremost cliffhanger example of a whole school of Hollywood film-making in the 40s that gloried in matchless pure entertainment.”

At the end of Kill Bill volume 1, there are RIP notices for Charles Bronson, Lucio Fulci, Sergio Leone, Shaw Brothers regulars Cheng Cheh and Lo Lieh, Django director Sergio Corbucci, Lee Van Cleef and the director of this serial, Willian Witney, who Quentin Tarantino has said is a lost master. Witney popularized shooting fight scenes in small bursts, allowing stuntmen to keep high energy throughout the scene. Some of his best regarded movies are The Crimson Ghost, Adventures of Captain Marvel, Master of the World and the very late in his career Darktown Strutters.

Spy Smasher was one of 26 Republic serials re-edited and re-released as a Century 66 film on television in 1966, in the midst of Bat-mania, and titled Spy Smasher Returns. Other films in this series include — thanks to ugglewuggle on the Movie Serial Message Boards — the following (the in parentesis title is the re-edited Century 66 title):

Darkest Africa (Batmen of Africa)
Undersea Kingdom (Sharad of Atlantis)
Robinson Crusoe of (Robinson Crusoe of)
Clipper Island (Mystery Island)
The Fighting Devil Dogs (Torpedo of Doom)
Hawk of the Wilderness (Lost Island of Kioga)
Mysterious Doctor Satan (Doctor Satan’s Robot)
Spy Smasher (Spy Smasher Returns)
Perils of Nyoka (Nyoka and the Lost Secrets of Hippocrates)
G-Men Vs. the Black Dragon (Black Dragon of Manzanar)
Secret Service in Darkest Africa (The Baron’s African War)
The Masked Marvel (Sakima and The Masked Marvel)
Tiger Woman (Jungle Gold)
Manhunt of Mystery Island (Captain Mephisto and the Transformation Machine)
Federal Operator 99 (FBI-99)
The Purple Monster Strikes (D-Day on Mars)
The Crimson Ghost (Cyclotrode “X”)
The Black Widow (Sombra, The Spider Woman)
G-Men Never Forget (Code 645)
Dangers of the Canadian Mounties (R.C.M.P. & the Treasure of Genghis Khan)
Federal Agents Vs. Underworld, Inc. (Golden Hands of Kurigal)
The Invisible Monster (Slaves of the Invisible Monster)
Radar Men from the Moon (Retik the Moon Menace)
Jungle Drums of Africa (U-238 and the Witch Doctor)
Canadian Mounties Vs. (Missile Base at Taniak)
Atomic Invaders (Atomic Invaders)
Trader Tom of the China Seas (Target: Sea of China)
Panther Girl of the Kongo (The Claw Monsters)

You can watch this on Tubi.