The movie opens with and 11-year-old girl and her mother standing by the subway waiting for it to arrive. Two men come and shove the mother, stealing her purse. The men climb on the subway and the woman and her daughter stay off. Just before the subway leaves one of the men shoots the mother. The young girl screams. We then see Sgt. Neil Craig run in and hug the young girl and we discover that this policeman is the girl’s father (Chris Cooper)
The next scene opens by showing a very unkempt apartment. We see Tyler (Robert Pattinson) on the porch smoking, and drinking. Tyler gets a call and quickly puts on a suit and runs out the door. He goes to a graveyard where his father (Pierce Brosnan) his mother (Lena Olin) and his sister (Ruby Jerins) are laying stones on a grave. The grave belongs to a Michael Hawkins. They go to a coffee shop and his mother remarks that Michael would have liked to know they still went to the coffee shop. The coffee shop was Michael and Tyler's special place. Tyler's sister Caroline begins to talk about an art exhibit she has when her father rudely interrupts her to ask for the sugar. Tyler yells at his father and runs out of the coffee shop. Before leaving he moves the sugar away from his father.
We see Tyler walking with his roommate Aiden (Tate Ellington). Aiden suggests selling a kit to girls who have one night stands. We learn that Tyler had a one-night stand the night before. Aiden tells Tyler to call the kit S.L.U.T. Tyler laughs at him but is obviously depressed. Aiden convinces Tyler to go out for "just one drink!" Tyler and Aiden party at the bar and leave completely drunk with two girls from Miami. Tyler sees a fight going on and he runs in to break it up. Tyler begins to smack one guy repeatedly, very violently. Aiden follows him to try to stop him and in the struggle Tyler hits one of the Miami girls in the nose. The police come and break up the fight and the other Miami girl tells the police that Tyler and Aiden are innocent. The police set them free and Tyler thinks that only two of the people involved should be arrested. He yells at the policeman (the same policeman we saw before played by Chris Cooper) that he's supposed to give a shit. The policeman tells him to go home. Tyler ends up hitting the policeman and the policeman slaps his face hard against the police car. Tyler and Aiden both go to jail and Aiden says that Tyler might want to throw his life away but he doesn't.
Aiden and Tyler's bails are both posted and Tyler goes to see his father. He says he'll pay the lawyers fee and that he doesn't want to be bailed out of anything. He also says "I didn't call you" meaning he doesn't want his father's help.
We see the policeman and his daughter (the young girl who lost her mother) portrayed by Emilie de Ravin. We learn her name is Ally. Her father drives her to school at NYU.
At the NYU campus we see Aiden arguing with a teacher over a grade and trying to flirt with her in order to improve his grade. He sees Ally and her father pull up and he recognizes her father from the night before. He runs home to tell Tyler and suggests that Tyler take her out on a date and then dump her or steal her panties and sell them as revenge for her father scarring Tyler's face. Aiden points her out to Tyler when they're back at school and Tyler recognizes her from his social policies class. (Earlier we had seen her answer a question about terrorism in Tyler's class.) He tells her he is doing an experiment with women in their early twenties to find out how much of an A-hole Aiden is. She says she's 19 and he offers to take her to dinner as the reward for being in the survey. She seems reluctant but accepts.
He calls her before he leaves to dinner and says, "I know you're going to stand me up." We see that this was her plan as she is in sweatpants on her bed. She lies and tells him she’s on her way and gets dressed in a hurry. Her father asks her where she's going and who she's going with (very overprotective.) We see them at the restaurant where she explains why she orders her dessert first. We learn she is constantly wary of death and has a fear of asteroids. They go to a fair and Tyler pays off a game attendant to get a panda for Ally. She gets into a taxi (she doesn't take the subway) and Tyler tries to kiss her. She says "Not tonight" and Tyler remarks that she eats her dessert first for fear of choking but won't kiss him before she drives off into the unknown. She interrupts him with a kiss and the taxi drives off.
Tyler picks up his sister Caroline from school and they go to Central Park where they discuss her bullies, her art exhibit and that she believes their father doesn't like her.
Tyler is making spaghetti for Ally on their second date. She notices pictures of Michael and that Tyler has a tattoo on his chest that says Michael. Tyler sprays Ally with water and they get in a water fight, eventually leading to a make out session in the shower. Aiden comes back and tells them to go to a party upstairs and have "just one drink."
The scene then cuts to Tyler holding Ally’s hair as she vomits over the toilet. She says to call her dad before she falls asleep but her cell battery is dead. Ally wakes up the next morning and her father has been searching all night for her overprotective. She knows how worried he gets and runs home and he yells at her for being out all night with a boy and coming home smelling like alcohol. She says he doesn't have to be on top of her just because he couldn't save her mother and he slaps her on the face and cuts her lip.
She runs off to Tyler’s house and falls asleep there. She wakes up and her and Tyler have sex.
Tyler leaves her to go to the coffee shop that was special to him and Michael and writes about her to Michael. When Tyler comes back he explains to Ally that he had to tell Michael about her.
Tyler has a birthday party at his mother’s house (he turns 22 the same age his brother was when he killed himself.) Caroline talks to Tyler, Aiden and Ally about her art exhibition. Tyler's mother worries that his father won't show up. Tyler says I won't let that happen and he invites his father to dinner with him and Ally before the art show. Ally asks Caroline if she minds Ally, a "random girl" coming to the exhibition. Caroline says, "You're not random. You're Tyler's girlfriend." During this conversation Caroline tells Ally that the Met is one of her favorite places in the world.
Tyler's father shows up late to dinner and they have a discussion about the Yankees. Ally tells Tyler and his father about when she saw her mother murdered. Tyler's father gets a call and says I have to go but I'll meet you at the exhibition. He stands up Caroline's exhibition and she is heartbroken.
Tyler takes Ally to his apartment and rides his bike to his father's office. We can tell he is furious. He runs into his father's business meeting and yells at him. He asks him why he isn't riveted by everything Caroline says. The clients of Tyler’s father offer to leave and he yells, "Sit the fuck down!" Tyler adds that the other children are going to hang themselves on his watch. (We had learned that Tyler's brother Michael hung himself after beginning to work for his father and Tyler’s the one who found his body.)
Tyler goes home crying and Ally tries to reassure him.
There's then a montage of scenes of Ally and Tyler being in love (going to the beach, etc).
We see Ally's father picking up the phone to hear a message from Ally saying she's all right.
Ally and Tyler are riding a train with Aiden who remarks that he has slept with a person from every country. Ally challenges him with an Eskimo and he goes to show her the Eskimo librarian he slept with while Tyler goes home.
Tyler hears something in his house and picks up a bat. He sees Ally's father sitting on his bed. (He traced the call and found Tyler.) Ally's father asks if Ally knows how Tyler got his scars. Tyler says no. Ally's father attacks Tyler and tries to strangle him and then leaves. Tyler breaks down.
Ally comes home and Tyler tells her the truth. She breaks up with him and goes home to her father.
Tyler takes Caroline to a slumber party. We see Caroline standing tentatively by the door, afraid to go in.
We see Ally at home giving her father cooking advice. Aiden comes to their house and says it was his fault that Tyler didn't tell Ally how he got his scars and why he was dating her and she should forgive Tyler.
We see Caroline calling her mother sobbing and begging to be picked up from the slumber party. At night some of the girls who had bullied her had sheared off half of her hair.
We see Ally and Aiden in Tyler's mother's apartment where she is sobbing. Tyler is lying on the bed with Caroline who is also sobbing. Tyler won't leave until she is asleep. Then Tyler and Ally go out to the porch and talk. Tyler’s father comes to comfort Caroline, which is surprising because no one thought he really loved her.
Tyler takes Caroline to school where she has a new haircut and the girl who cut her hair remarks that she likes it. Tyler shoves the girl’s desk and throws a fire extinguisher out the classroom window.
Tyler goes to jail for vandalism and his father posts his bail. Tyler's father says he is taking care of the bully problem at Caroline’s school. He asks Tyler to come to his office the next day to talk to the lawyers. Tyler says again that he didn't call him.
Tyler spends the night with Ally and leaves her a note saying he'll be back.
Tyler's father doesn't expect Tyler to show up on time so he goes to take Caroline to school. When Tyler calls him and says he is at the office he is surprised and tells him to wait. Tyler sits in his father’s chair and notices that the screensaver on his father's computer is pictures of their family. Tyler didn't realize his father cared that much.
We cut to a teacher writing the date on the board at Caroline’s school, September 11 2001.
We see Tyler looking out the window of his father's office as if he heard something. The screen moves back and we see that Tyler is in the 92nd floor of one of the twin towers. The shot fades to black.
We then see..
Tyler’s mother, Caroline, and his father run outside sobbing.
Ally and Aiden confusedly run to the roof of their building and burst into tears.
Ally's father instructs other policemen near the twin towers while sobbing.
We see Tyler's journal among the rubble.
Cut to Caroline leaving stones on Tyler's grave and we hear a voiceover of Tyler saying he forgives Michael for killing himself. We see Tyler’s father taking Caroline to the Met, one of her favorite places in the world. We see Aiden with a tattoo on his arm that says Tyler. Then we see Ally waiting on the subway platform where her mother was murdered. She gets on the subway for the first time in years and smiles as the credits roll.