Secret Code Chapter 7: Submarine Signal - ComicWeb Serial Cliffhanger Theater

This serial introduces us to the WWII scenery, when a superhero tries to prevent Nazi agents from stealing a secret formula. The spy ring is led by fifth columnist Rudy Thyssen, who is trying to get possession of this top-secret formula the United States had developed for manufacturing synthetic rubber. Then, Police Lieutenant Dan Barton stages a public dismissal from the police department, in order to join the saboteurs ring and learn their secret code they have been using, creating explosive gases and artificial lightning to sabotage the exhausting war effort. To further assist his efforts, Barton assumes the secret identity of the Black Commando, a masked man who is wanted both by the villains and police, who (allegedly) are also searching for Barton for a murder charge. Finally, Barton attempts to steal the formula and is captured by Thyssen and put under the protection of the sabotage ring. Joining the gang, he learns of their plans, which he immediately leaks to his girlfriend Jean Ashley. After innumerable troubles and lost efforts in trying to decipher the enemy's secret codes, our hero thinks that the villains could be annihilated by the tried and true method of having their escaping submarine rammed and destroyed. As an aggregate value, at the end of each thrill-packed episode the audience is given a short lecture on solving complex secret messages.

text from wikipedia

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