A short story [cuento] always tell two stories [historias]. In the classic short story, there is a visible story that has another secret story embedded inside of it. At the end, the secret story comes to the surface, producing an effect of surprise. The two stories often operate with two different "systems of casuality." The key elements function for both the presenting and the secret story. The modern short story, according to Piglia, "abandons the surprise ending and the closed structure; it works the tension between the two stories without ever resolving it, telling "two stories as if they were one."
Piglia, Ricardo. "Theses on the Short Story." New Left Review 70. 2011. https://newleftreview.org/II/70/ricardo-piglia-theses-on-the-short-story