Throughout “The Story of an Hour,” there are several hints that foreshadow Louise Mallard’s death from heart failure at the end of the story. The first line of the story reads:
Knowing that Mrs. Mallard was afflicted with a heart trouble, great care was taken to break to her as gently as possible the news of her husband’s death.
Right away, readers learn that Louise has “heart trouble,” and that any powerful emotion or shock—in this case, learning that her husband, Brently, was killed in a railroad accident—could harm her health.
After Louise briefly weeps over Brently’s death, she locks herself in her bedroom and goes through a range of emotions. At first, she’s exhausted from crying. But then, as she realizes that Brently’s death means that she’s finally free to “live for herself,” she becomes increasingly excited:
Now her bosom rose and fell tumultuously. [...] She said it over and over under her breath: “free, free, free!” The vacant stare and the look of terror that had followed it went from her eyes. They stayed keen and bright. Her pulses beat fast, and the coursing blood warmed and relaxed every inch of her body.
The reader can filter this reaction through the context of Louise having a weak heart and infer that Louise is putting her health at risk by surrendering to the excitement that she knows she’s supposed to avoid because of her condition. Thus, her labored breathing and quickening pulse foreshadow her heart attack at the end of the story.
Louise’s heart condition is also perhaps why her sister Josephine eventually comes upstairs and begs her to open the door:
“Louise, open the door! I beg; open the door—you will make yourself ill. What are you doing, Louise? For heaven’s sake open the door.”
The illness she’s referring to here could be Louise’s weak heart, again hinting at Louise’s imminent death.
Finally, at the end of the story, it’s revealed that Brently is actually alive:
Some one was opening the front door with a latchkey. It was Brently Mallard who entered, a little travel-stained, composedly carrying his grip-sack and umbrella. He had been far from the scene of accident, and did not even know there had been one. He stood amazed at Josephine’s piercing cry; at Richards' quick motion to screen him from the view of his wife.
There’s another brief moment of foreshadowing here, when Richards tries to “screen [Brently] from the view of his wife,” likely because he knows that the shock of seeing Brently alive could kill Louise. And indeed, right after this, the narration reveals that Richards is “too late”—Louse has died of a heart attack.
