A teacher who has always led a quiet, monotonous life is thrown into turmoil by the murder of a young woman who had been staying with him for several months.
One evening, in fact, the protagonist finds himself home alone, as his wife has gone out to play cards with friends.
The girl returns home, gives an absent-minded greeting, and goes straight to her room.
In the morning, she is found dead.
The suspicions of the police, as well as those of the neighborhood, turn immediately toward the man.
The protagonist sees his world collapse; he feels ostracized by the community, whose members felt bolstered listening to the pastor's words, writes Simenon:

they felt they were the law, they were justice, every new sentence uttered over their heads made them stronger, while Ashby, in their midst, grew weaker and more isolated

.
The police also delve into the protagonist’s past, discovering that his father was a drunkard who squandered the family fortune before committing suicide.
This inquiry casts the protagonist back to the anguish of his youth—to the prospect, that is, of becoming like his father:

what struck him was not so much this or that particular vice, a definite danger; what drew him was something vague, belonging to certain quarters of big cities, to certain streets, certain lights, even certain smells

.
The fear of being inexorably drawn toward vice and depravity had driven him to seek security, peace, and order, to the point of marrying a woman for whom friendship prevailed over passion.
Feeling unjustly accused, abandoned by friends and community alike, along with the resurfacing of his past, are elements that bring this fatal attraction back into the open, shattering the shell the protagonist had fashioned for himself.
Inexorably, as if driven by a fateful force, the protagonist murders a young woman, committing the very crime of which he had been falsely accused.
This is only ostensibly a detective story.
In truth, Simenon masterfully outlines the falsehood of life within a hypocritical community that ambiguously casts out one of its members merely because he is suspected of a crime.
To everyone, it seems only natural that Ashby had become infatuated with the girl and killed her in a fit of murderous passion.
Yet Simenon’s skill also lies in crafting a protagonist torn between two opposing forces: social order and the lure of lust and violence.
When the rules of social coexistence—in which the protagonist believed and which had served as a bulwark against his own impulses—dissolve and reveal their utter vacuity, he gives free rein to his true inclinations.
A profoundly relevant theme is thus explored: the relationship between communal ties and the complexity of individual feelings and dispositions.
The crime is nothing more than the catalyst for a polarity rooted both within society (solidarity versus hypocrisy and confinement) and within the individual (the pursuit of peace and stability versus the urge toward transgression).

The Death of Belle