The Fat Man (1946-51)

The Fat Man, a popular radio show during the 1940s and early 1950s was a detective drama based on characters by Dashiell Hammett. It starred J. Scott Smart in the title role, as a detective who started out anonymous but rapidly acquired the name 'Brad Runyon'.

Broadcast from the studios of WJZ in New York, the series premiered on the ABC Radio Network on Monday, January 21, 1946, at 8:30pm, as part of a block of four new programs (I Deal in Crime, Forever Tops, and Jimmy Gleason's Diner). Based on Dashiell Hammett's fiction, The Fat Man was further developed by producer, E.J. ("Mannie") Rosenberg. The program was directed by Clark Andrews, creator of Big Town, and Charles Powers. The main writer was Richard Ellington, with other scripts by Robert Sloane and Lawrence Klee.
-wikipedia.org

Episode: Murder Squares The Triangle