What is the theme of the story "The Sire de Malétroit's Door"?

One of the most important themes of this beguiling short story is the fragility of human existence. Throughout the story, the protagonist Denis de Beaulieu veers back and forth between security and danger, creating a constant tension that provides the story with its own unique rhythm. Just as Denis can never truly relax, neither can we. And there's a lesson for us all there: however comfortable we might feel in our own little lives, potential disaster lurks around every corner.
The same applies to Denis, even after the threat of his being hanged is lifted. Though a superficial reading of the story might lead one to expect that he and Blanche will live happily ever after, such a judgment cannot be sustained, either in the light of our own experience or on the basis of the action leading up to the story's ostensibly sunny denouement.