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.
Initial Situation
The storm begins and Calixta's family is separated.
In a classic beginning, danger lurks from that old menace, Mother Nature herself. The man of the house, Bobinôt, is away from home and can't protect his wife. Readers are given the impression that a woman is alone and possibly in danger back at the ranch. This scene is a lot like the tornado at the beginning of The Wizard of Oz, setting the stage for what's to come.
Conflict
Calixta's old lover arrives at her house just in time to be trapped there by the storm.
It would be one thing if Calixta had to wait out the storm alone in the big house, worrying about her husband and small son being in danger out in the storm. But she's not alone: as soon as the storm starts, a cute guy rolls up – a guy she has a history with. That's a complication waiting to happen!
Complication
Calixta and Alcée are reminded of their past flirtation.
As we were just saying, this conflict is a complicated one. First Alcée shows up and keeps Calixta from being alone. While it's technically OK for them to be alone together from a societal standpoint (they're both married, and it's a cyclone), it's pretty clear they both feel a little weird about it. That weirdness is compounded when they start having flashbacks to the more physical interludes they had in the past. Once they start remembering their attraction to another, it's a slippery slope to acting on that attraction again.
Climax
Calixta and Alcée have sex.
We realize that putting this scene in this category is a bad pun waiting to happen. It's impossible to avoid, though, since this is the most exciting part of the story, the part where the characters are either approaching or coming down from their high point. Both the story and the characters reach their high points at the same time here. It's rare that this element of the plot is played out so literally in fiction, but it happens from time to time.
Suspense
Calixta's family returns home just after Alcée leaves.
Here we wait with bated breath. Will Bibi and Bobinôt get home before Alcée leaves? Will they cross paths? Will Calixta be able to cover up what has just happened? For his part, Bobinôt worries over whether Calixta will be angry with them when they return home. It's a state of worry about a possible set of repercussions or punishment – but it all turns out to be just fine.
Denouement
Alcée writes to his wife and tells her she doesn't need to rush home.
Here we see the aftereffects of the previous scenes, as Alcée reacts to his affair by telling his wife that she can stay away longer on her vacation. While he presents his request as a favor he's making on her behalf and as proof of his love for her, we readers know he's doing it not because he's selfless, but because he just got laid. Luckily, his wife is cool with getting more downtime before coming back to her marriage.
Conclusion
Everyone benefits from the affair, and no one finds out about it.
The story is thus neatly tied up in a bow. No one's going to find out about all the action that just happened. Alcée and Calixta's secret is officially safe, dissipating just as the storm itself has. Whether the other characters suspect some change is a separate issue. At the ending of the story, everything is fine.