The Whistler narrates tales of crime and wrongdoing. At the beginning, he tells us, "I the Whistler know many things, for I walk by night. . . . I know many secrets hidden in the hearts of men and women who have stepped into the shadows." He then proceeds to that episode's story, occasionally making editorial comments along the way. In most episodes, the protagonist comes to a (richly deserved) bad end.
The show ran from 1942 till 1955, making it one of the longer running crime shows. As with many long-running radio shows, a number of actors portrayed the Whistler, the one recurring character, over they years. The episodes that I've listened to have been well-scripted and -acted with good production values.