Death is so powerful in "The Story of an Hour" that even news of someone else's death, if told the wrong way, can be lethal. Finding out someone hasn't died can be almost as powerful, and deadly, too. This story is unusual in that it allows a character to explore the feelings beyond grief or loss that one might have if a loved one died. Mrs. Mallard's complex reaction to the news of her husband's death speaks to the terrible, almost welcome freedom a tragedy can bring. Ultimately, the fact that death is coming seems certain. It's the question of who gets taken away by death, though, that changes so drastically.
Mrs. Mallard's death at the end of the story suggests that her ideas about freedom were just delayed shock, and that she was in fact so grief-stricken her death was only a matter of time.
The passing of a second character to replace the misreported fatality of a first recalls, in its irony, the idea of being unable to escape Death when one's time has come.