The mood in "The Story of an Hour" is essentially pessimistic. Kate Chopin's favorite author was the great French short story writer Guy de Maupassant. His influence can be seen in many of her works. She was fluent in French and translated a number of his stories into English. The mood of "The Story of an Hour" can be highlighted by comparing it with Maupassant's most famous short story, "The Necklace."
Mathilde Loisel is unhappy at the beginning of "The Necklace." Then she experiences a brief period of radiant joy when she is admired and sought after at the minister's ball.
She danced with rapture, with passion, intoxicated by pleasure, forgetting all in the triumph of her beauty, in the glory of her success, in a sort of cloud of happiness comprised of all this homage, admiration, these awakened desires and of that sense of triumph which is so sweet to woman's heart.
But her joy turns into far greater unhappiness when she loses the borrowed necklace.
Kate Chopin's "The Story of an Hour" (an hour of freedom and happiness based on a false illusion) follows a similar pattern. Louise Mallard is grief-stricken when told that her husband was killed in a railroad disaster. But then when she is alone she begins to realize that her loss had unforeseen benefits. Now she is free of the slavery of marriage, of the degradation of being used for her husband's sexual pleasure without regard for her own feelings and wishes. She experiences a mood of joy and liberation, like a bird that has escaped from its cage.
She arose at length and opened the door to her sister's importunities. There was a feverish triumph in her eyes, and she carried herself unwittingly like a goddess of Victory. She clasped her sister's waist, and together they descended the stairs.
But then comes a shock comparable to the shock of horror felt by Mme. Loisel when she realizes that she has lost the diamond necklace. Just as Matilde faces a life of drudgery and penury in Maupassaant's "The Necklace," so Louise Mallard faces a life of dependency and marital slavery when her husband Brently comes home like a ghost returned from the dead.
So the predominant mood is one of boredom and spiritual deadness, brightened for an hour by an illusion of freedom and joy, and then exposed as an impossible dream for any woman in that time and place.
When the doctors came they said she had died of heart disease--of joy that kills.
Matilde Loisel lives for many years and grows coarse and ugly. Louise Mallard dies instantly--not of joy but of extreme dismay. Which of the two women has the better fate?