Chopin's theme is freedom and confinement. How does she use her characters, the setting, the plot, and symbols to get her message across?
As far as setting goes, it is very limited, and this seems to mirror the confinement Louise Mallard has evidently felt in her married life. The story takes place within the confines of the Mallards' home, the vast majority of it in one particular room. Louise locks herself in her room after she hears the news of her husband's death; however, one window is open in that room, and, through it, she sees that everything outside is "all aquiver with the new spring life." This window is a symbol of the renewed life that Louise has gained now that she is a widow (or so she believes). She is now excited about the possibilities her life holds, and she seems very alive to the beauty of life now that it is truly her own to live.
Spring days, and summer days, and all sorts of days . . . would be her own. She breathed a quick prayer that life might be long. It was only yesterday she had thought with a shudder that life might be long.
She will no longer have to compromise or concern herself with the will of her husband, a man who she admits loved her but who was legally entitled to rule over her. The "repression" that is, apparently, responsible for the "lines" on her young face no longer exists, and her old life seems washed away by the "delicious breath of rain . . . in the air" outside. The window represents her freedom, and the new life outside represents her new life as a free woman.
There are also few characters in the story, and Louise spends so much of the story by herself in her room that the sense of her life as being a relatively confined one—similar to the limited setting—seems to be confirmed. Richards, her husband's good friend, comes quickly in order to break the news to Louise gently, and we get the sense that people typically try to protect Louise due to her diagnosis of heart trouble. Such protection, while well-meaning, can feel stifling, and so we see Louise attempt to escape it by escaping Josephine and Richards almost as soon as the news is broken. "She would have no one follow her" to her room.
We see, then, through the plot, how the behavior of even well-meaning people can feel confining. Louise needs to be alone, away from her sister and her husband's friend, even though they are only trying to help and protect her. Louise knows, also, that "she would weep again when she saw . . . the face that had never looked save with love upon her, fixed and gray and dead." Brently Mallard has not been a terrible husband: there's been no abuse or cruelty or even a lack of love—at least, not on his side. Despite the fact that their behavior toward Louise has been affectionate, she is still so glad to escape it, to be free of them.