Air Force captain Roger Drum (Buster Crabbe) is to complete a flight to South Africa under the identity of a spy who is to make contact with a subversive "mystery group." Drum crashes, and for a while has no idea who he is, but at first the "reds" see him as their comrade. Since Drum is able to peal a sacred gong he is heralded by the primitive, all-white "rock people" as the heroic "Thun'da," and runs around in a loincloth. Drum/Thun'da first appeared in a brief comic book series -- sub-titled "King of the Congo" -- before Columbia turned it into a minor serial with highly familiar elements. In addition to those nasty reds, who are after a radioactive mineral, there is a group of Cavemen ruled by the corpulent if powerful Kor (Rusty Wescoatt). There is a native princess named Pha (Gloria Dea) and a High Priest (William Fawcett) who wears a long, silly wig and can witness future events in his crystal ball! There's also a cute chimp who acts like Cheetah at times but is never given a name. There's a comical scene when henchman Andreov (Rick Vallin) is "tortured" by a lamp and headphones playing jazz! The best cliffhanger has Thun'da trapped in quicksand while nasty natives keep chucking spears at him and try to push a log away before he can grab hold of it and save himself. Crabbe has dark hair for this picture.
Verdict: Not one of the more memorable Columbia serials and Crabbe's last. **.