The Mystery Squadron (aka Mystery Squadron) is a 1933 American pre-Code 12-chapter Mascot film serial, directed by Colbert Clark and David Howard. The film was produced by Nat Levine, and stars Western star Bob Steele, Guinn “Big Boy” Williams, Lucile Browne, Purnell Pratt and Jack Mulhall. Mascot Pictures, in The Mystery Squadron made an impressive serial using a great deal of aerial footage to enliven the action.

Plot
At an air show, ace flyers Fred Cromwell (Bob Steele) and his partner, Bill “Jelly Bean” Cook (Guinn “Big Boy” Williams) perform aerial feats that prove they are the greatest aviators around. A dam being built by Stephen Gray (Lafe McKee), the owner of a construction firm, comes under attack from the mysterious pilot, the “Black Ace”, and his “Mystery Squadron” of pilots. With Gray facing financial ruin, he asks Henry Davis (Jack Mulhall), the dam foreman and ex-stunt pilot to hire Fred and Bill.

The identity of the Black Ace is so secret that it is even concealed from his own men in the Mystery Squadron. Fred and his partner, Bill seek to identify the Black Ace and stop his attacks on Gray’s construction of the power dam. The Mystery Squadron is headquartered in a secret cave near the dam.

A rich gold mine is threatened by the dam’s construction and a number of individuals behave suspiciously, including Lafe Johnson (Purnell Pratt), a rival contractor, Martin (Edward Peil, Sr.), the hotel owner, Collins (J. Carrol Naish), a construction employee for Gray and Dr. Flint (Robert Frazer). When the Mystery Squadron strikes again, Fred finds Davis tied up in his car. Davis explains he has been held captive by the raiders.

Fred and Bill finally confront Davis with evidence that he is the Black Ace. Davis panics and takes off in his aircraft only to be shot down by Fred and his partner.

Cast
Bob Steele as Fred Cromwell, old stunt pilot friend of Henry Davis
Guinn “Big Boy” Williams as Bill “Jellybean” Cook, old stunt pilot friend of Henry Davis
Lucile Browne as Dorothy Gray
Jack Mulhall as Henry Davis, dam foreman and ex-stunt pilot
Purnell Pratt as Lafe Johnson
Robert Frazer as Dr Flint
J. Carrol Naish as Collins
Edward Peil, Sr. as Martin
Bob Kortman as Bracken
Lafe McKee as Stephen Gray