This episode, The Marvin Thomas Entry, originally aired June 8, 1948.
Mr. Keen, Tracer of Lost Persons was one of radio’s longest running shows airing from October 12, 1937 to April 19, 1955, continuing well into the television era. It was produced by Frank and Anne Hummert. The sponsors included Whitehall Pharmacal (as in Anacin, Kolynos Toothpaste, BiSoDol antacid mints, Hill’s cold tablets and Heet liniment), Dentyne, Aerowax, RCA Victor and Chesterfield cigarettes. It aired on the NBC Blue network until 1947, when it switched to CBS. 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). However, only 59 of those 1690 Mr. Keen programs are known to exist. The cliches, stereotypes and simplistic dialogue of the show provided much fodder for Bob and Ray’s memorable parody, Mr. Trace, Keener Than Most Persons, broadcast in numerous variations. It was also satirized by Harvey Kurtzman and Jack Davis in Mad’s fifth issue as “Kane Keen!”
The character of Mr. Keen was referenced by Alfred Hitchcock in one of his television shows. Mr. Keen is also mentioned in the stage version of Bye Bye Birdie by the character Mr. Harry MacAfee, who was played by Paul Lynde.