From the 1920s to the 1950s, radio was the entertainment source for millions. Two of the primary themes of radio serials were mysteries and adventure. This is a detailed analysis of the important programs in these genres - ""Jack Armstrong,"" ""The Green Hornet,"" ""Sergeant Preston,"" ""Tom Mix,"" and more. Each entry includes type of series, broadcast days, air dates, sponsors, network, cast and production credits, and a comprehensive essay. When, as often happened, the series landed in other media, that is examined as well.