17 yo Shawna's parents split 10 yrs ago when her mother moved to New York with her lesbian lover. Relations between Shawna and her mom were always strained but blew up entirely when Shawna almost died from a ruptured appendix due to her mom's neglect when she was 14. She has refused to talk to her since then.
Her father, a doctor, is a controlling vindictive bully. He refuses to let her date an Asian boy, then a boy whose father owns a bar, then another because he is Protestant. He opens her mail and takes away her computer and cancels her phone service just to prove he's the boss. He has already planned Shawna's future and refuses to consider that she should be anything but a doctor herself. She is actually a good artist, but that's what Shawna's mom was, so there is no way he will let her follow that path. He and most of his family are derogatory towards gays so Shawna picks up their attitude as well.
Then mom's partner Fran calls to say that mom has had a stroke and may not survive. Shawna flys to New York to wait alongside Fran and her 2 sons. The prognosis is grim but Fran wants the doctors to treat her aggressively.
Then dad shows up with an old living will saying "no heroic measures." However, I question this plot device. They lived in Cleveland but dad was in San Francisco at a conference at the time. He flies directly from California to New York but he just happens to be carrying the living will with him? He also claims to hold a medical power of attorney, giving him decision-making authority, although the doctors never ask to see it.
Dad decides to pull the plug immediately over Fran's objections. When he finds out she was in the process of converting to Judaism, he returns her body to Cleveland and holds a Catholic funeral for her.
Fran and her sons attend the funeral, as well as some of their gay friends. Shawna is openly rude, calling one of them a "dyke." She also makes a stupid comment about gay men adopting little girls. Her best friend LeeLee tells her she is acting just like her Aunt Colleen, who Shawna has always considered to be her most vicious relative. Shawna gets jealous because LeeLee makes friends with Tova (the adopted girl).
Because mom never updated her will, dad inherits everything, which lets him force out Fran from their house. They (conveniently) move to Cleveland. Dad forbids her to have any contact with them, but when she does anyway, he wants her to get back some jewelry and photo albums that Fran has.
Fran acts suspiciously and doesn't want to give Shawna some of the baby photos she wants, so Shawna swipes them. When she shows them to dad, he tells her they aren't pictures of her. They look like her but they are actually Fran's younger son. Then dad does the math and realizes that his wife could have been pregnant when she left and that Schmule could really be his son. So a DNA test and a custody hearing later, and dad has the son he has always wanted.
Shawna has become friends with Ayre, Fran's older son, and is miserable about what havoc she has created. She defies dad by sneaking Schmule (now called Sam) to see Fran and Ayre.
She now remembers walking in on her parents having sex right before mom left. Since she was only 7 it didn't make sense to her at the time, but she now realizes that dad was raping mom (he was holding her down and saying "Can Fran give you this?" while mom was crying and trying to push him off). So she is now more sympathetic to mom for leaving.
LeeLee finally tells Shawna that she and Tova are more than just friends; she had held off letting her know because of her derogatory comments on gays. She intends to move to New York and live with Tova after high school. Shawna snubs her, leading to a further rift between them.
Dad thinks everything is wonderful but Shawna thinks that Schmule is showing suicidal tendencies. Things come to a head when she returns Schmule to Fran then finally confronts her father.(less)