Mrs. Louise Mallard is the protagonist and practically the only character in "The Story of an Hour," a short story written by Kate Chopin. We learn two things about her in the beginning: she is married to Brentley Mallard and she has a heart condition which causes people to break bad news to her gently.
When the story begins, her sister and a family friend come to see Louise, and they tell her that they have confirmed that her husband has died on a train wreck. Of course Louise's immediate response is to fall to the floor and wail, but after a moment she recovers and goes up to her room.
Here we discover what Louise is really reacting to. Like so many of the married women of her time, Louise is in a marriage which is more like a prison than a relationship. While her husband loves her, he decides everything for her; while he wants her to be happy, he does not allow her the freedom to make her own choices in life. Although Louise loves her husband sometimes, she can only think about his death in terms of what it will mean to her future. She says to herself:
There would be no one to live for during those coming years; she would live for herself. There would be no powerful will bending hers in that blind persistence with which men and women believe they have a right to impose a private will upon a fellow-creature. A kind intention or a cruel intention made the act seem no less a crime as she looked upon it in that brief moment of illumination.
Given these feelings, then, it is not surprising that the word Louise Mallard keeps whispering to herself is "free, free, free!" This is an indication of the new life she can have now that she is not confined by marriage.
Of course we know how the story ends, so her feelings of exhilaration are short-lived; however, for a few moments, anyway, Louise feels free.
For more expert analysis on this and other stories, check out the excellent eNotes sites attached below.