A writer named Glen Whitman wrote about the concept of the two things. The two things refers to the type of question that is often posed in a bar after a couple of drinks. "What are the two things everybody needs to know about X?" For every subject there are only two things that are really important. Everything else is an application of those two things or else not important.
I decided to try it with some aspects of writing. Here, in my opinion, are the two things a writer needs to know about plot.
1. Isolate the protagonist.
2. Grow the problem.
I recall seeing a fantasy poster once by the great calendar artist Frank Frazetta. In it a warrior woman, sword in hand, stands on a clump of rock, maybe the top of a mountain, surrounded by a more numerous, better-armed enemy. The "ah ha" was when I realized I was looking at the climax of this woman's story. I don't recall the story or the character, but her future was clearly in doubt at that point. The print was a perfect metaphor for what takes place at the climax of a story, the peak of the action.
Isolate the protagonist.
The insight for me came when I asked, "How did she get there?" She didn't get up that morning with the idea of climbing a rock by herself and swinging a sword at an army of bad guys. She probably had family, friends, comrades-in-arms. Where were they? Why weren't they helping her? What made her go it alone? I don't think she wanted to go alone. Clearly some of our protagonists are loners, but it's not always by choice. When it comes to our own survival, most of us want some help and backup. Readers of police procedurals know that the call that gets cop cars rolling is "Officer needs assistance." This warrior may have sent such a call, but the assistance never arrived. Had help arrived, the story would not be as compelling.
Grow the problem.
How did these bad guys get there? How did they get to be so numerous? How did they get to be so well-armed? Our warrior must have royally pissed someone off. She probably didn't start the day that way. Like most of us, she had problems, but they would have been small ones. None of us want to take on more than we can handle. When things begin to get out of hand, we tend to back off. Obviously, our hero didn't. Her problem grew and she could not escape it.
Isolate the protagonist and grow the problem.
Both of these happen slowly and inexorably in the story. We know before we open the book where the hero will end up--alone and up to her neck in trouble. The hero could be FBI agent-in-training Clarice Starling, in a basement catacomb, in the dark, trying to save a young woman from a serial killer with a handgun and night-vision goggles. She started the day as the junior member of a team. Her job was to gather evidence. Along the way, she became isolated and her problem grew.
Even the quintessential loner heroes like Jack Reacher and John McClain don't start alone. Nor do they set out to fight terrorists in a skyscraper. On the other hand, when the story involves an ensemble such as the men and women of the Dan Kearney Agency, one of the group will end up alone in the final battle.
To get our hero to that peak of the action where he or she stands alone, we must build in events that increase our protagonist's isolation each step of the way and grow the problem, like Audrey the carnivorous plant, right before everybody's eyes. If we do that, the anticipation that something bad is going to happen will increase inexorably.
So, the two things about plotting are isolate the protagonist and grow the problem. Everything else is an application of those two things or else not important.
Look for my collection of Val Lyon mystery stories, Game Face, on Kindle, Smashwords, and other ebook platforms or in paperback from Barnes and Noble or Amazon.