Based on Robert W. Chambers' bestselling 1906 novel The Tracer of Lost Persons, Mr. Keen, Tracer of Lost Persons proved to be one of the longest lasting radio mystery programs, airing 1690 episodes over eighteen years, from October 12, 1937 to April 19, 1955. It's nearest competitor was Nick Carter, Master Detective, which aired a measly (!) 726 broadcasts. Less than five dozen episodes are known to have survived.
For the first six years the program ran 15-minute episodes three times a week on the NBC Blue Network. In December 1943, the show expanded to a weekly half-hour format on Thursday evenings at 7:30. Eventually, a paucity of missing persons forced Keen to take on more criminous cases as a private eye.
Mr. Keen, Tracer of Lost Persons was created for the radio by Frank and Ann Hummert, a prolific and not so discerning couple who had created over 125 separate radio programs. The Hummert's programs were noted for low wages, overworked actors, stilted stereotypes, hasty writing, and a large dose of melodrama. Audiences love them.
"The Case of the Moonless Night" stars Bennett Kilpack as Mr. Keen and Jim Kelly as Keen's assistant Mike Clancy. It aired on January 12, 1944 and was the sixth (and earliest surviving) show in the half-hour format.