What is the central irony of "The Story of an Hour"?

There is one central irony in Chopin's short story "The
Story of an Hour". The main character, Mrs. Mallard, is a woman who feels the stress of
being a repressed wife. As a woman, the lines of her face show her to be much older than
she really is. The stresses of her life have pre-maturely aged and overwhelmed
her.

Upon learning of the death of her husband, Mrs.
Mallard locks herself in her bedroom to think about the path her life will take. She
looks out the window and notices the renewal that nature brings and begins to embrace
herself as a free woman.

Soon after her epiphany, Mrs.
Mallard emerges from her bedroom "like a goddess of Victory." Unfortunataley, and
ironically, Mrs. Mallard's joy comes to an abrupt end. Mr. Mallard has not died in a
train accident. Instead, he was not even at the site of the accident and is
alive.

Here is where the story hits its ironic twist. After
seeing that her husband is still alive Mrs. Mallard dies- on the spot. The irony of the
story exists given that her husbands "death" allows her to find her freedom. Upon the
realization that her freedom does not really exist, Mrs. Mallard succumbs to the fact
that she is, again, a bound woman. This new epiphany kills her.