You asked two questions and I can only answer one according to enotes regulations. This story by Kate Chopin really isn't that long, so I would encourage you to read it to gain a sense of what happens, but for a basic summary read on.
We are presented with Mrs. Mallard who is "afflicted with a heart trouble" and whose husband has just been killed in an accident. Her sister tells her and is rather worried about the impact of this news. Mrs. Mallard initially shows great grief, and then locks herself in her room. As she looks out of the window and contemplates the death of her husband and her new state, she begins to feel incredibly liberated and whispers to herself the words "free, free, free!" Although she loved her husband and genuinely mourned him, she would be able to "live for herself now." As she contemplates her new life she opens the door to her sister and as she goes out of her bedroom she has a look of "feverish triumph" in her eyes. She goes down the stairs to be surprised by her husband who had not been in the accident. Mrs. Mallard drops dead with the shock.