Edited version of the 1940 Universal serial "Flash Gordon Conquers the Universe", released in a syndication package to TV in 1966.

Skipper Murphy is serving as trainer and inspiration for his brother Red Murphy training for a world championship title bout. Trouble comes for the Murphys when Red runs up against a gambling syndicate and is put on the spot to throw the fight.

A remake of Frank Capra's Submarine (1928), Devil's Playground is a snappy Columbia "B plus" picture starring Richard Dix and Chester Morris. Submarine officers Dorgan (Dix) and Mason (Morris) battle on land for the affections of dance-hall girl Carmen (Dolores del Rio). She marries Dorgan but makes a play for Mason when her husband is on duty. The romantic rivalry is forgotten when Dorgan must rescue Mason and his crew from a sunken sub.

In order to give up her life of crime and go straight, renowned jewel thief Sophie Lang fakes her own death and retires to London. She soon finds a job as a companion to a wealthy old lady who is also a jewel collector. One day her employer decides to take an ocean trip to the US, taking Sophie with her. She also takes along a $200,000 diamond, which she locks up in the ship's safe. Of course, the diamond is soon stolen from the safe. A reporter also happens to be aboard the ship, and he has had his suspicions about who Sophie really is. Sophie has to find the real thief and recover the jewel before the ship docks in New York, because an investigation could reveal her true identity.

After saving himself from hanging, Laramie Nelson saves Tracks Williams from the same fate. They then travel to Lindsay's ranch where they get jobs. There they run into Adams who they learn is planning to rustle Lindsay's horses.

Suspected crime boss Nate Girard beats a murder rap, and newspaper photog Kent Murdock is on the story. Girard and lawyer Redfield throw a party for the news men where Murdock romances a mystery woman who confronted Girard in front of him, but Murdock's fiancée Hester shows up. After they return to his apartment, have a fight, and she leaves, the mystery woman slips in and begs for his help. Police Inspector Bacon and the cops show up, looking for the mystery woman; Murdock hides her. Murdock goes with the cops to discuss the murder the woman is suspected of. Bacon explains (in flashback) how some photogs were setting up a shot with Girard and Redfield. When the flashbulbs popped, Redfield keeled over dead and the woman, Meg Archer, fled while the newsmen ran out to phone their papers. The newsmen (who were rounded up later as thoroly as possible) are taken into police custody, except for Murdock (who wasn't at the scene), who is given a cap on the sly by rival McGoogin. Altho ...