George M. Carleton

An airplane carrying a pair of police officers escorting gangsters to prison crash-lands in the African jungle. They are rescued from an attack by savage natives by a white woman who appears out of nowhere, and it turns out she is a lost heiress who herself crash-landed in the jungle years before.

A Martian invader crashes his spaceship conveniently close to the workshop of a scientist who is developing an interplanetary craft. If the extraterrestrial Purple Monster can complete the rocket ship and return to Mars, he will be able to start a full-scale invasion of Earth. Good thing Craig Foster sets out to thwart the Monster's mission!