Cox Jim Cox 
Mr. Keen, Tracer of Lost Persons [PDF ebook] 
A Complete History and Episode Log of Radio’s Most Durable Detective

That "kindly old investigator, " Mr. Keen, sought missing persons and unraveled crimes longer than any other fictional detective ever heard or seen on the air. For 18 years (1937-1955) and 1690 nationwide broadcasts, Keen and his faithful assistant Mike Clancy kept listeners coming back for more. The nearest competitor, Nick Carter, Master Detective, ran for 726 broadcasts. This definitive history recounts the actors and creators behind the series, the changes the show underwent, and the development of the Mr. Keen character. A complete episode guide details all of the program’s 1, 690 broadcasts.