An alien from Mars crash lands on Earth. Astronomer and scientist Dr. Cyrus Layton (James Craven) is looking through his telescope that night and sees it. At first he thinks it is a meteorite. He goes to check out the crash site and finds what looks like a man dressed in a space uniform. The man says he is from Mars. The man appears friendly. He takes the alien home with him. It's not till later that he calls himself the Purple Monster (Roy Barcroft).

The Purple Monster is aware that Layton is working on a spaceship. Layton calls it a Jet Plane. Layton shows him his designs for the ship. Then the Purple Monster tells Layton about his real reason for being on Earth. He plans on using Layton’s plans to construct a fleet of Jet Planes so that Mars can invade Earth and enslave it.

The Purple Monster then kills Layton by using what he calls a carbo-oxide gas. He says that it is a concentrated pellet containing Martian atmosphere, harmless to him, but deadly for Dr. Layton. The Martian then takes over the doctor’s body. Disguised as the doctor the alien can go about doing evil deeds and planning for the invasion. He manages to fool Layton’s niece Sheila Layton (Linda Stirling) and Craig Foster (Dennis Moore). Craig is a former secret service agent that is currently working for the foundation that provides funds for Layton’s project.

A gangster named Garrett (Bud Geary) has been trying to extort money from the professor. The Purple Monster convinces Garrett that it would be financially advantageous to join him as his number one henchman. With his help, and a few minions recruited by Garrett, the Purple Monster begins using Layton’s plans to build his own jet plane.

Craig finds out about the Purple Monster and continues to foul the up his devious plans. The Martian continues to try to destroy Craig using some rather involved methods. Eventually the Purple Monster’s disguise is penetrated. But Craig won’t give up until the Purple Monster is foiled for good.

“The Purple Monster Strikes” was released in 1945 and was directed by Spencer Gordon Bennet and Fred C. Brannon. The film was one of twenty-six Republic serials re-released as a film on television in 1966. The serial was then cut to about 100 minutes and re-titled “D-Day on Mars”.

If you have seen other Republic serials and you’re feeling a little déjà vu there’s good reason. The Purple Monster costume was re-used in “Flying Disc Man from Mars” 1950, “Commando Cody: Radar Men from the Moon” 1952 and “Zombies of the Stratosphere” 1952. Stock footage from “The Purple Monster Strikes” was also re-used in these serials. The rocket crash footage was re-used for Flying Disc Man from Mars. The alien Marcia’s costume was reused as Lara's outfit in the "Superman On Earth" episode of the “Adventures of Superman” television show.

The original production title for the serial was “The Purple Shadow Strikes”. “The Flying Disc Man from Mars” 1950 is sort of a sequel to “The Purple Monster Strikes”. Budgets being as low as they are for serials I can understand reusing props, costumes and film footage. I’m not sure how long the alien was on Earth, but it would have been nice if the wardrobe department had more than one dress for Shelia.

I understand that plot devise is important and, in serials, difficult to come by since most of them have at least 12 to 15 chapters and you need something to keep things going, but for an alien that can take over a dead person’s body, (ick) and has gas pellets that contain the atmosphere of their planet, they should have been able to come up with a spaceship that does not crash.

A couple things that we’ll just gloss by, when Craig and Shelia go into the office to retrieve the hidden camera, didn’t they see poor dead Uncle Cyrus just sitting in a chair? Also how long can a Martian use a dead body before it starts to, well, get ripe?

One other tidbit. The space ship is called a Jet Plane. Reason being, "spaceship" was a relatively new term at the time and Republic wasn’t sure if they would have any flack from Universal. Their recent Flash Gordon serial used Rocket Ship as part of the title for their movie version of the serial “Flash Gordon: Space Soldiers”.

CHAPTER TITLES: 1. The Man in the Meteor; 2. The Time Trap; 3. Flaming Avalanche; 4. The Lethal Pit; 5. Death on the Beam; 6. The Demon Killer; 7. The Evil Eye; 8. Descending Doom; 9. The Living Dead; 10. house of Horror; 11. Menace From Mars; 12. Perilous Plunge; 13. Fiery Shroud; 14.The Fatal Trail; 15.Take-Off To Destruction.