Nadine Franklin, a seventeen-year-old high school junior in the suburbs of Portland, has tempestuous relationships with her popular older brother Darian and her image conscious mother Mona, and only felt close to her father Tom. Tom died of a heart attack when Nadine was thirteen, leaving her best friend Krista the only person keeping her buoyed.
At Nadine’s home, Nadine and Krista get drunk while Darian throws a pool party. Nadine falls asleep and Krista goes downstairs and talks to Darian. The next morning Nadine finds Krista giving a handjob to a naked Darian in bed, straining their friendship. The next day they run into each other at school and Darian asks Krista to be his girlfriend. Nadine feels desperately alone and turns to her classmate Erwin Kim, who has a crush on her, though Nadine is attracted to older student Nick Mossman.
Darian invites Krista to a house party, who insists Nadine join. There, Krista is introduced to other students, leaving Nadine on her own. After failed attempts at mingling, Nadine sits outside with another partygoer, who remarks how inferior Nadine seems compared to her brother, and Nadine leaves the party. She invites Erwin to an amusement park, where his attempt to kiss her is rejected. They still finish their date, and at the end of the night Nadine tells him he is a great guy and they become close friends.
At school, Krista confronts Nadine for ignoring her, and Nadine tells her that Darian does not care about her and will soon drop her, to which Krista retorts by saying he asked her to be his girlfriend and to prom, which is months away. Nadine makes her choose between herself and Darian. Krista does not want to choose, and Nadine angrily ends their friendship.
Mr. Bruner becomes Nadine’s source of support at school and he admits that she is his favorite student. Nadine has become lost due to not seeing Krista and one night Erwin calls Nadine who hangs up on him. Nadine calls him back soon after and invites herself to go swimming in his pool, much to his excitement. Nadine learns that he is rich after showing up to his house and that he is an animation filmmaker and accepts his invitation to their school’s short-film festival.
Driving to school, Mona and Nadine have a fight that leads to Mona bringing Nadine with her to work. There, they argue about her father, and Nadine steals Mona’s car and drives away. She writes a sexually explicit text to Nick, and accidentally sends it when trying to delete it.
Nadine confides in Mr. Bruner she is going to kill herself, and he tries to reassure her. She receives a reply from Nick asking her to hang out. Mona calls Darian, telling him that Nadine is missing and Darian leaves to find her. On their date, Nick repeatedly attempts to have sex with Nadine in his car. Embarrassed and heartbroken, Nadine runs away and calls Mr. Bruner, who drives her to his house where they wait with his wife and infant son until Darian arrives. Darian tells Nadine that he has been suffering from the pressures of taking care of the family in their father’s place. Darian confesses that he feels trapped and did not apply to colleges far away because he has to be there for the family. And it upsets him that Nadine doesn’t like his relationship with Krista who is the best person in his life. Nadine confesses her own feelings of self-hatred, intensified by her envy of Darian. They hug, ending their feud.
As Nadine leaves for the film festival, she is met by Darian and Krista; the friends reconcile and agree to catch up later. Realizing that Mona is still worried she has run away, Nadine texts her that she is safe, and Mona decides to trust her word. Erwin’s animated film is revealed to be a story about an alien boy who falls in love with a girl at high school but is rejected. Nadine apologizes to Erwin for taking so long to accept his love. Erwin is congratulated by his colleagues, and introduces Nadine, who greets them with a smile, finally opening up to others.