When scientist Dr. Cyrus Layton (James Craven) witnesses a meteorite fall, he rushes to the area to investigate. What he finds is not a piece of space rock, but rather the crashed vehicle of a Martian. The otherworldly visitor introduces himself as the Purple Monster (Roy Barcroft), the first strike in an impending Martian invasion of the Earth. The Purple Monster says that the one thing the Martians lack is a safe, reusable rocket ship to travel back and forth between planets, and it seems Dr. Layton has just designed one. The Purple Monster possesses the body of Dr. Layton and, using an army of criminal henchmen led by Garrett (Bud Geary), he sets out to acquire the necessary materials to build a prototype rocket ship. The only people standing in his way are Dr. Layton's niece Sheila (Linda Stirling) and criminologist Craig Foster (Dennis Moore).
This ridiculous-yet-fun serial is rare in that the villain is the main character. I'm not sure why his name is "the Purple Monster". It seems like an odd name for somebody, even a Martian. In the second half of the serial, he sends for help from back home, and Marcia (Mary Moore) arrives to assist. That's right...Marcia the Martian. The Purple Monster has a variety of skills and weapons from Mars to help in his efforts, but he often just uses a revolver and his fists.
The hero of the piece, played by Dennis Moore, is bland and completely forgettable. Linda Stirling is easy on the eyes, but her acting isn't much. The movie was still enjoyable for the well-done action scenes, the groan-worthy cheats at the chapter breaks that alter prior events to save the protagonists, and for the camp sensibilities of the Purple Monster, his pal Marcia, and their boss, the Emperor of Mars. Serial enthusiasts may notice that much of this serial's footage was later reused in other serials of the late 40's and early 50's.