The whole subplot is how the mother tears apart her family because of her borderline personality disorder. The father has checked out by going to live wiith his girlfriend while the two kids are left alone to deal with their mothers manic depressive episodes. The mother places her son in charge of making her feel better by being her surrogate husband and caretaker.
What unfolds for her son is his downward spiral with self hatred and self harm through the use of drugs to escape his pain. The daughter emotionally checks out but finds surfing provides her wiith the only peace she's ever known. The brother and sister, twins, share the love of surfing, but the brother is ensnared too closely with his mother's mental illness to stand a chance at life.
Jennifer garner does a wonderful portrayal of a woman with borderline personality. It's a car wreck you can't turn away from. Wonderfully, tragic, sad story.