The Earth is attacked by unknown forces. As people everywhere watch the world's great cities fall, Los Angeles becomes the last stand for mankind in a battle no one expected. It's up to a Marine staff sergeant and his new platoon to draw a line in the sand as they take on an enemy unlike any they've ever encountered before.

Feature version of the 1936 movie serial of the same name, with altered music scoring, released outside the USA only until 1950.