That kindly old investigator, Mr. Keen, Tracer of Lost Persons, sought missing and murdered individuals longer than any other fictional detective ever heard or seen on the air. For 18 years (1937-1955) Keen and his faithful assistant, Mike Clancy, entertained followers with their intuitive perception that kept listeners coming back for more. With 1690 nationwide broadcasts, Mr. Keen was the most resilient private detective in a namesake role. The nearest competitors were Nick Carter, Master Detective (726 broadcasts), The Adventures of Sherlock Holmes (657) and The Adventures of the Falcon (473). This book presents a portrait of both the beloved character and the venerable dramatic series. An introductory chapter examines the significance of the sleuth in American entertainment. A concerted effort is also made to properly define each Keen era and an appendix provides an episodic log of the program's 1690 broadcasts.