The Purple Monster Strikes

The Purple Monster Strikes 1945 is a Republic Movie serial. It was also released as a Century 66 television film under the title DDay on Mars 1966.

Astronomer Cyrus Layton is working late one night on his new airplane design in his observatory. He witnesses what he believes is a meteorite landing in the far distance. He contacts his niece Sheila and asks her to bring Craig Foster to the observatory to help analyze his discovery he then sets out to search for the meteorite crater. Layton instead discovers a crashed spaceship the ships pilot emerges and explains that he is from the planet Mars.Mistakenly thinking the alien is friendly, Layton takes him back to the observatory. Once there the Martian, calling himself The Purple Monster, wishes to see Laytons designs for the new airplanespaceship. He proudly shows the alien his designs until the alien explains that he is now stealing them, to build a spaceship for himself to fly back to Mars, where a fleet of the ships will then be used invade the Earth. When Dr. Layton objects, the Martian murders him with a weapon that emits a carbooxide gas, which kills instantly. The alien then transforms into a ghost and takes over Dr Laytons body. Doing so fools the astronomers niece Sheila and criminologist Craig Foster, both of whom work with Dr. Laytons foundation, which is responsible for commissioning the spaceship project. ........

Source: Wikipedia