A young man befriends the last surviving Civil War veteran, intending to rob him of $50,000.

A mad scientist named Dr. Satan plots to steal key pieces of technology to enable him to build an army of robots based on his prototype to conquer America. The only one standing in his way is Bob Wayne, who fights Satan as the enigmatic Copperhead. Mysterious Doctor Satan is a 1940 film serial named after its chief villain. Doctor Satan's main opponent is the masked mystery man, "The Copperhead", whose secret identity is Bob Wayne, a man searching for justice and revenge on Satan for the death of his step-father. The serial charts the conflict between the two as Bob Wayne pursues Doctor Satan, while the latter completes his plans for world domination.

A prison trustee rescues a despondent executioner from a bar-room brawl, and is blamed for the fight by a tabloid reporter who actually started it, and loses parole, becomes embittered, and gets blamed for murder of guard.

An undercover agent wrongly punished for murder is paroled to a remote tropical island with a diamond mine slave labor run by a sadistic foreigner.

"The Unknown" was the final entry in Columbia’s I Love A Mystery series. A woman hires two detectives to keep her alive long enough to claim her inheritance.