Seven-year-old Annabella rides home with her mother after an amazing, sunny day at school. Her great day only heightens her optimism of the future. Unfortunately, when she arrives home, she is met with the news that her parents' marriage is ending. Annabella never thought she'd hear the word "divorce" in reference to her mom and dad. Their religion strictly forbade it. Yet, because of her egotistical mother, Ronda and her prideful father, William, that's exactly what was happening.
Ronda, a once admired and beautiful woman, refuses to take any of the blame for the demise of the marriage. She is instantly determined to ruin William for leaving her. She begins wasting all her assets in her attempts for revenge. It begins to consume her to the detriment of both her own mental well-being as well as that of her offspring.
William is a successful businessman and a high-standing member of their Jehovah's Witness congregation. He has a reputation to uphold. His alcoholism, brought about by his two tours in Vietnam and the childhood abuse at the hands of his father, have become more apparent and the close relationship he once had with Annabella begins to change drastically. Unfortunately, his persistent inner demons and feelings of betrayal won't allow him to provide the type of guidance and structure he knows his children truly need.
Ronda resents Annabella for the love she still has for her father and she urges Annabella to follow suit with her two older siblings in their demonstrated hatred for William. Ronda continues physically and emotionally abusing Annabella while holding the other children in a much higher regard. Annabella wants to hold everyone together while Ronda seems either nonchalant or oblivious to how the split is affecting them all.
William's new relationship sends Ronda over the edge. Despite her ongoing attempts, she never gets the revenge nor the reintroduction to the riches and the social status she was so desperately looking for over the years. Ronda is no longer the envy of the members of the congregation and she remains plagued with the small-town stench she swore she'd rid herself of since she was a child.
Ronda's abuse of her daughter comes to a head but teenaged Annabella finally finds the strength to break free from her mother's personality-disordered wrath. Annabella feels guilty for not being able to save and heal her broken family. She vows to never allow her own future marriage and children to suffer the same fate. The Last Magnolia is Annabella's reflection upon an eternally darkened view of herself as well as one of the world she once knew.