Zydereen of Neptune

Zydereen of Neptune may be considered a TV movie. It is a compilation of three 1955 episodes of the Flash Gordon serial. The episodes are titles "The Witch of Neptune," "The Brain Machine," and "Struggle to the End." Zydereen is the witch, and she's messing with the oxygen generator on Neptune. Flash Gordon must find and stop her before the oxygen runs out! (Thanks, WTM!)