MICHAEL SHAYNE "Phantom Gun"

August 6, 1948. https://en.wikipedia.org/wiki/Michael_Shayne_(radio_program)
Michael Shayne, "the reckless, red-headed Irishman" was a popular hard-boiled detective created by American crime novelist Brett Halliday.
Phyliss Kenny had hired Michael Shayne to find out if her husband was two-timing her. He wasn’t but he’d gotten himself mixed up with a character named Jasper who was following his usual routine of getting close to his blackmail victim by working for him. In this case he was the gardener at the Duval estate and that’s how Dick Kenny got mixed up with him, Dick was the Duval chauffer.
The second version was a transcribed program with Jeff Chandler in the title role. Don W. Sharpe was the producer. This version, was set in New Orleans. The program was produced by Searles & Parks Inc. Bill Rousseau was the director and syndicated.