In every story your protagonists (and antagonists) will face problems that need to be solved. How it gets solved matters to the storyteller.
For instance, the antagonist may have on his desk a big red button marked, "Destroy The Earth" that sits alongside another big green button marked, "Release Imprisoned Protagonist." Boy is it embarrassing when he gets those two mixed up. What's most embarrassing to the storyteller is that the reader doesn't find out until AFTER the antagonist pushes the wrong button that the he is red-green color blind.
The problem for the antagonist is knowing which button to push. The problem for the storyteller is justifying to the reader why the antagonist would have such a stupid set of buttons on his desk.
In olden days, an actor playing the role of a god (deus) would be lowered by a crane (machina) onto the stage whereupon he would tie up all the loose threads of the story. This storytelling device has a name Deus Ex Machina. If you're going to do this, you have to have the crane tested beforehand. Its gears cannot squeak and the wires holding the actor aloft need to be hidden.
In olden days, revising a story was a Big Deal. You'd have to slaughter a new sheep for a fresh piece of parchment then recopy the scroll. Or if you used a typewriter, adding pages in the early parts of the story threw off your page numbers.
Nowadays, not so much.
I was reading
this post just now wherein J.M. Van Horn complains about a specific instance of a badly executed Deus Ex Machina. I'm a bit sympathetic toward the unnamed writer whose clumsiness justifiably earned Mr. Van Horn's wrath. We all find ourselves written into a corner from time to time and wonder how to get out. You get out with a word processor that adds foreshadowing scenes earlier in the narrative.
As I commented there, it is not hard to insert a few scenes to introduce the Deus Ex Machina. If you're going to say, "and then a nuclear war started" in the 3rd act, you'd better foreshadow it or you'll earn
MY wrath as a 3rd act fail. Adding that foreshadowing isn't particularly hard to do. Just write a couple
scenes to introduce the character, then insert them into early
chapters.
The foreshadowing scenes can be used to heighten tension.
Consider Agatha Christie’s “Nemesis.” Miss Marple faces a deadly confrontation with the murderer at the end of the story. Since Marple is a little old lady in her pajamas, she can hardly use ninja kung fu to protect herself. She is a cozy detective. She cannot be an action hero (
unlike Sherlock Holmes). She needs a hard-boiled detective to lend her some muscle to subdue the murderer.
Easy. Add a private-eye with a gun who steps out of the shadows.
If Christie introduces the private-eye right there at the end, it constitutes a clumsy Deux Ex Machina fail. But she didn't. She introduced the private investigators--two of them--in the first act. At the beginning of any mystery, there's always going to be a bunch of suspicious looking characters the reader is looking at and wondering whodunit. So, Christie adds two more. Perfect.
Now, it gets better. Instead of just providing a pair of hot gats and hard fists, Christie makes these private investigators right proper red herrings. After introducing these two women Christie shows these two stay close to one another and seem always to be conspiring about something. ("Are they lesbians?" the reader wonders. Or vengeful school chums of the murdered girl?) Moreover, these two suspicious looking characters are following Miss Marple.
This is what I like best about fiction, showing the reader something that has two equally plausible explanations: Private Eyes and Murder Suspects can do the same things for completely different reasons. Only you the writer keep one of those explanations carefully hidden or unexpected.
FEMALE private eyes? That's man's work! Nobody would expect FEMALE private eyes!
Note that Christie has turned a potential clunk in the 3rd act into a delightful surprise. How much work did it take to write? Not much. Just a few scenes here and there. With a word processor, you don't have to worry about parchment or retyping pages.
This is where the writer's creativity manifests itself. Christie could have put Sam Spade or Mike Hammer on the bus at the outset of the tale to provide hard fists and a hot gat, but she added girls with guns. Everybody likes girls with guns. And everyone likes more red herrings at the outset of a whodunnit.
When you see an obvious Deus Ex Machina in a story, I believe it is a lack of storytelling skill or bad (nonexistent) editing. Just revise the earlier chapters to foreshadow the appearance of the unexpected character who solves a big problem in the 3rd act. Shame on the editor who doesn't insist upon this.
When Christie did it, she used two female private investigators. Your story may work completely differently. Your SF novel may require an alien who beams in at the last minute with a BFG-9000 and an intergalactic arrest warrant. OK, just remember that he doesn't have to be introduced to the reader as a galactic crime-fighter. He can be introduced to the reader as an annoying clerk who is insistent that the TPS report go out with its cover sheet. Or maybe an insistent process server the protagonist has been avoiding.
And maybe the BFG-9000-weilding alien has some completely different agenda, but its appearance gives the protagonist what she needs to gain the upper hand with the antagonist. This is where your creativity has a chance to shine. Go for it!
