704. THE MYSTERY SQUADRON (1933-USA). 12 Episode Mascot Serial. With BOB STEELE, “BIG BOY” WILLIAMS, J. CARROL NAISH. A stunt pilot and his Jelly-bean chomping sidekick are hired by a construction company to fight the “mystery squadron”, led by the unseen “Black Arp” TryÂing to keep a dam from being completed to save their gold mine, the squadron of biplanes, flying out of a hidden cave, sabotages the dam with aerial flame throwers and other foul means. The serial conÂtains some excellent stunt flying in addition to the usual two-fisted serial action. Who is the “Black Ace? 22S minutes.