Mr. Keen was one of radio's longest running detective series, a prime-time mystery with serious soap opera trappings. Coming from the radio fiction factory of Frank and Anne Hummert, it employed all the stereotypes, heavy dialogue, and the trite plotting of its daytime cousins. Like the later Mr. Chameleon, Mr. Keen solved his cases with a minimum of logic, often through coincidence, twists of fate, slips of the tongue, and guilty knowledge expressed by the culprits.