He's the bad guy--no, HE'S the bad guy--no, THAT GUY is the bad guy!

A lot of the individual stories from the hero pulps such as the Shadow, Doc Savage, the Spider, and so on depended on the identity of the master villain being a mystery until the last page or two of the tale. In the better stories, this was often done by making it a fair-play mystery, seeding subtle clues to the villain's identity throughout the story.

That way, if you've figured it out, you get to shout a satisfying "I knew it!" If you didn't figure you, you get to shout out a still somehow-satisfying "Oh, man, how did I miss that?"

Another method--and an equally valid one if the story is well-written and honestly exciting--is to give us no real clue at all to the villain's real identity, then club us over the head with it at the last moment.

This can seem like a cheat, but if the revelation makes sense when all is explained, then it is still dramatically viable and allows us to give an oddly satisfying shout of "Him? You're kidding?"

The March 1936 issue of Doc Savage had our hero and his companions going up against "The Metal Master." The villain here runs a ruthless criminal organization, but what makes him really dangerous is his secret weapon. He has a device that allows him to melt metal without generating heat or damaging anything else around the metal. It's a device that gives the villain enormous power--he could use it to disarm soldiers and destroy tanks and planes enmasse.

A man bringing this information to Doc is murdered, but Doc is soon on the trail. What follows is one of Lester Dent's typically entertaining and fast-moving adventures. Doc follows up clues; he allows himself to be captured to gain information, then escapes; he avoids assassination attempts and tricks the bad guys in various ways. His best trick is convincing the thugs to voluntarily carry a potential booby trap with them back to their secret base on a remote island.

Much of the early story takes place in New York City, but there's also things happening aboard the Innocent, a schooner sailing out of Havana. The captain of this craft also has plans for the metal-melting machine and is holding Doc's friend Renny and another guy hostage. So there is actually two groups of bad guys in play, each trying to kill Doc as well as wipe out each other. Eventually, everyone involved ends up on the remote island, where Doc and his men seem to be outnumbered and outgunned. But Doc often has the upper hand before most of us even realize that hand has already been dealt.

During this story, we simply don't know who the Metal Master is, even though we can be confident he (or she) is one of the characters we've met. But during the course of the story, at least five different characters are identified by someone as the Metal Master. There seems to be a pretty broad clue at one point who it is,  but even that could be a red herring. Many readers will probably guess the real identity of one other of the suspects before the novel ends, but that still leaves the question of who the Metal Master may be.

Well, when we find out, we discover that Doc has known for some time, but he had information that wasn't shared with us. So there's no way we could have known!

But that's okay. This isn't a fair-play mystery and its not meant to be. It's an adventure story with a number of clever and exiting action sequences and a number of cool plot twists. There's no way we could have known for sure who the Metal Master is, but we still have fun getting there.