An escaped criminal, known as Harry Crowl, but preferring to be called by his prison number 39013 (pronounced Thirty Nine - O - Thirteen), seeks revenge on the man who sent him to prison, millionaire philanthropist Horace Granville. He kidnaps Granville, imprisoning him within his own house, and disguises himself to take Granville's place, as the frail old man in a clean room, necessary for his health. The only other person allowed past the glass barrier being his doctor. He then sets about methodically destroying everything Granville owns. When we enter the film, he has already destroyed a number of Granville properties, and has set his sights on the Granville Amusement Centre, at which a trio of acrobats is performing. The daredevils, Gene, Bert, and Tiny escape but Gene's kid brother is badly wounded in the blaze, and later dies of his injuries. Seeking revenge they take jobs as private investigators for the man they believe to be Horace Granville. Through a series of deadly traps, and with the help of a mysterious cloaked figure, known only as "The Red Circle", the daredevils begin to unravel the truth.
In the first chapter, we are introduced to all the above facts, and even shown the secret room within the Granville estates where 39013 is keeping the real Granville. He is kept in a cell, the exact duplicate of the one in which 39013 resided for his abruptly ended sentence. This room is trapped, so that in the event that 39013 does not return, a dripping reservoir will run dry. The loss of weight will tip the scale, causing deadly gas capsules to break upon the floor, killing Granville in a very short time. This causes him to spout the characteristic line, "You best hope I continue to live, Granville."
Charles Quigley as Gene Townley, high diver, one of the Daredevils of the Red Circle
Herman Brix as Tiny Dawson, strongman, one of the Daredevils of the Red Circle
David Sharpe as Bert Knowles, escape artist, one of the Daredevils of the Red Circle
Carole Landis as Blanche Granville, Granddaughter of Horace Granville
Miles Mander as Horace Granville, millionaire philanthropist victim, and ex-partner, of 39013
Charles Middleton as '39013' (Harry Crowel), escaped criminal with a vendetta against Horace Granville
Daredevils of the Red Circle was budgeted at $126,855 although the final negative cost was $126,118 (a $737, or 0.6%, under spend). It was the cheapest Republic serial of 1939 and one of only three pre-war serials to be made under budget. The other two were The Fighting Devil Dogs (1938) and Mysterious Doctor Satan (1940). It was filmed between 28 March and 28 April 1939. The serial's production number was 897.Ironically, David Sharpe, who is generally considered to have been one of the greatest stuntmen in the movies, had to be doubled in action scenes by Jimmy Fawcett because he was playing a leading role, and the studio could not risk any production delays were Sharpe to suffer injury.