One of the better serials. A mystery squadron of fliers led by the Black Ace is attacking a dam that is under construction by Stephen Grey (Lafe McKee) and his daughter Dorothy (Lucile Browne). The foreman Hank Davis (Jack Mulhall) hires his flier friends Fred (Bob Steele) and Jellybean (Guinn Williams) to help protect the mine...
But they soon run into trouble with the fiendish Black Ace and his team of fliers who possess biplanes with flamethrowers! Thanks to hidden panels and rooms seemingly everywhere the Black Ace always seems to be one step ahead and his identity remains a mystery...
It is of course break neck action with plenty of stunts and cliff hangers. The plot may have more holes than the skin of a biplane that has been in combat but the story moves so quickly there isn't time to dwell on it!