Dashiell Hammett's most famous detective took to the radio airwaves from 1946 to 1951 for 245 episodes over three networks. This Sam Spade was a pretty loose version of the Hammett character, but the Hammett name helped the popularity of the series. Hammett's name, however was removed from the series in the late Forties during the Communist witch hunt of that time. Played by Howard Duff, and, from November 1950 until the series' close, by Steve Dunne (because of Joe McCarthy's anti-Communist hysteria, Duff was not invited to play the role for the last 24 episodes), Spade was a less tough and more wise-cracking character. Lurene Tuttle played the ever-loyal secretary, Effie.
The Adventures of Sam Spade won an Edgar Award for Best Radio Drama from the Mystery Writers of America in 1947.
In "The Vaphio Cup Caper" Spade is hired to protect a valuable, but Sam is knocked out. Wakening, he finds the cup gone and a dead body. More danger awaits Sam before he closes this
BTW, Evan Lewis featured this episode on his highly recommended blog, Davy Crockett's Almanack, back on Halloween day, 2009. So consider me a Johnny-come-lately.