The weed of crime bears bitter fruit. Crime does not pay.
One of classic radio's greatest icons began as a promotion that failed to promote. Detective Story Magazine was having a slump in sales, so they funded a promotional radio series using their stories. (The philosophically inclined might be interested to note, incidentally, that the magazine was one of Wittgenstein's favorites; and he more than once insisted that it was less a waste of time than reading philosophy journals. He at one point told a correspondent that it was beyond him why people read Mind when they could read Detective Story Magazine, since if philosophy is pursuit of wisdom, you can't find it in Mind but you might find it in a detective story.) To do this they needed a narrator, and they came up with The Shadow, who was little more than a sepulchral, sinister voice. The radio series was a smash hit -- and failed to boost sales. When they looked into the matter, the discovered that, simple as the magazine title was, people wouldn't remember it. Instead of asking for Detective Story Magazine they'd ask for The Shadow detective magazine. But, of course, The Shadow wasn't in the magazine -- he was just narrating, for radio, magazine stories with which he had nothing to do. But the people didn't want random detective stories -- they wanted The Shadow.
Faced with a problem like that, you can either cut your losses or adapt to what people actually want, so the publishers started up The Shadow Magazine that everyone had been disappointed to find didn't exist. And, since the radio version of The Shadow had been so effective that he had succeeded in getting people to try to hunt down a magazine that didn't exist, he continued on radio as well as in the pulps. At first he was mostly used as a narrator on various programs; but then a new series was begun.
The two versions diverged almost immediately, in part because the media had very different kinds of restrictions. In the pulps, The Shadow is sort of super-noir detective, a burglar-vigilante in black whose modus operandi is using mind games to terrify criminals into submission. But they discovered immediately that within the constraints of a thirty-minute radio program this wasn't enough. A pulp story can go into detail about The Shadow's intricate strategems and tactics to avoid detection; this is simply not possible on radio, and you can't just leave it all unexplained because that would be too confusing. So they hit on a solution: The Shadow could become invisible and project his voice, because he had learned the power "to cloud men's minds" while traveling in East Asia. He could hypnotize people into not seeing him. It was the perfect move for the character who was, in real life, more than anything, a Voice; by the power to cloud men's minds that is precisely what he becomes in the stories, as well, to great effect.
A similar simplification occurred in the case of The Shadow's identity. The pulps could afford to play bait and switch with The Shadow's identity, but this was just not suitable for the radio. So all of it was reduced to one, Lamont Cranston, wealthy playboy. Likewise, the pulps could afford to proliferate characters, but radio could not -- radio is a quite restrictive medium for characters, much more than print or television, because you have to keep all of the voices distinct and recognizable, since that is the only way anyone can distinguish characters at all on the radio. (This is an ongoing feature of radio drama, and many of the more interesting moves in radio were governed by it. It's how, for instance, we got Sergeant Joe Friday of Dragnet; how do you have a radio show about an entire police department? By having Everyman take all the different roles in the department, now in traffic, now in vice, now in narcotics. So Joe Friday remains the same, and the department itself changes around him from episode to episode.) One of the more interesting features of The Shadow in the pulps, in fact, and one of the few things about him that is more interesting than The Shadow on radio, was that he impressed peopled he saved into helping him fight crime -- if you were saved by The Shadow, The Shadow might be calling on you for a favor someday. This would have made the radio episodes too unwieldy. So they kept Lamont Cranston's police commissionar uncle, and they kept Moe "Shrevvy" Shrevnitz, who was the most important and likable of the pulp secondary characters, and, eventually, they invented a character to be The Shadow's associate and right hand, Margot Lane. She had to be a woman because they needed someone who would be a clear vocal contrast without being a distraction. She was modeled after Brenda Frazier -- the original celebutante, ancestress of all the Paris Hiltons ever, 'famous for being famous', and also famous because she knew how to play the media perfectly -- which was not, perhaps auspicious, but she was also modeled on Margot Stevenson, a successful stage actress who did indeed play her. Lane worked so well in radio that she began to be written into the print versions (as 'Margo' rather than 'Margot'). But even here we see the difference: the radio Margot had to be in on The Shadow's secret, whereas in print Margo Lane was the Lois Lane (but she was so before Lois Lane was invented).
If The Shadow sounds a lot like a superhero, it's because superheroes were partly modeled on The Shadow. Batman (or Bat-Man, as he was then) was originally a rip-off of The Shadow, particularly in his print version, so that even the early stories are pretty clearly based on some of the more popular Shadow stories. He only takes on a distinctive character through his interaction with a rather different kind of criminal.
The actor who first played The Shadow in the series was the 22-year-old Orson Welles. I don't think it's Welles's strongest role, and he only was in it for a year. He left to do The Mercury Theatre on the Air, one of the greatest of the great radio series, so it was a good move. He was replaced by Bill Johnstone for five seasons, then Bret Morrison, then John Archer, then Steve Curtleigh, then Bret Morrison again, who then played the character until the series ended in 1954. Different fans of the series will pick different actors as The Shadow; most people will pick Orson Welles, but my own view is that this is mostly because he was Orson Welles, and my own personal preference is Bill Johnstone. Welles can pull off a good Voice, but the radio Shadow needs to be able to pull of Lamont Cranston as well, and I think Johnstone does a better job of this -- it's certainly the case that Johnstone's Cranston is a stronger character than Welles's. But there were also some differences that had nothing to do with either actor: The Shadow was toned down a bit to make him more likable, and while Welles had the sinister vigilante who had no qualms about killing bad guys down, Johnstone was much better suited to playing a version of The Shadow who always found a way to bring people to justice without killing them.
There are various good Shadow episodes. One that's probably a general fan favorite is "The Temple Bells of Neban" from the Orson Welles episode. The one I've chosen, though, is "The Laughing Corpse" from 1940, in which The Shadow is played by Bill Johnstone. It lacks some of the pizzazz and mysticism of some of the common fan favorites, and unlike some of the more straightforward ones, the solution to the mystery is actually not an important part of the story, and on its own is rather pedestrian. But it is a well-liked episode, and I think this is because the crime itself, which is a series of murders, is so strange, and the deaths, which we hear, are so chilling, that it really doesn't matter what the explanation is. In fact, I think it ends up being a strength of the episode that they don't strain to make it a clever explanation; it would have just seemed silly and would have distracted from what makes the episode work.
You can listen to "The Laughing Corpse" here at My Old Radio.