Most good stories start with a fundamental list of ingredients: the initial situation, conflict, complication, climax, suspense, denouement, and conclusion. Great writers sometimes shake up the recipe and add some spice.
Exposition (Initial Situation)
There's Gonna Be a Murder
This stage of the plot sets up what's about to happen, even though in this case, the reader already has been told that a murder has taken place in the small Kansas town. The upstanding and unsuspecting Clutters are going about their typical daily routine in a chapter titled "The Last to See Them Alive." Two petty criminals have hatched a scheme to rob them and leave no witnesses. The criminals, Perry Smith and Dick Hickock, make their way from a town 400 miles away, and their car pulls up silently to the Clutter home late at night.
Rising Action (Conflict, Complication)
On the Run
The action here rises really quickly. The murders are discovered and the killers are on the run. But who's this? Agent Alvin Dewey, with his crack four agents and a taste for justice! The deed is done, but Dewey is on Dick and Perry's trail. The lawmen vow to solve the case but don't have any real leads. Meanwhile, the killers start to worry that they can't possibly get away with what they did. The plot tension mounts as the agents pursue lead after fruitless lead.
Climax (Crisis, Turning Point)
Floyd
A former cellmate of Dick's reads about the murders in the papers and knows whodunit. He'd worked for Herb Clutter and told Dick that he kept a stash of money in a safe. Dick immediately tells Floyd how he plans to rob and kill the family. Will Floyd snitch on Perry and Dick and risk getting killed for being a rat? He can't! He mustn't! Well, for some bucks and an offer of parole, turns out that he will. Floyd turning state witness is the turning point of the story, because without him, there wouldn't be a story. Or, at the very least, there would be an entirely different story.
Falling Action
I'm going to get you, Floyd.
With Floyd's testimony, Dewey and his agents slowly close in on Dick and Perry over a period of six weeks. The two men are captured, stand trial for the murder of the Clutter family, are found guilty and sentenced to hang. It's a long wait. While they wait, the readers get to hear the horrible details of the night of the murders. We've waited 264 pages for them.
Resolution (Denouement)
What Ends the Story and How it Ends
At the gallows, Dick forgives his executioners and Perry makes a short speech against capital punishment. After the two are executed, in cold blood, Agent Dewey shares a poignant moment in the graveyard with Susan Kidwell, now a beautiful young woman. Susan represents the future, and the future looks happy and bright. End scene. (See "What's Up with the Ending" about whether this scene ever really occurred.)