Filmed June-July 1941.The second of Bela Lugosi's 9 Monogram features, and the first of two with the East Side Kids.
Production notes indicate George Pembroke was cast as Dr. Von Grosch, but he was replaced by Dennis Moore.
The copyright expired and was not renewed, so the film fell into "public domain", meaning that virtually anyone could copy it and sell it without having to pay royalties. That's why there are so so many shoddy, badly cut, grainy copies of it on the market, put out mainly by companies that specialize in public-domain films.