Nicole Walker (Reese Witherspoon) is a fairly innocent teenager with a rebellious streak who is sent out from her mother's house. She lives in the suburbs of Seattle with her well-meaning but overbearing father Steven (William Petersen) and his new family: second wife, Laura (Amy Brenneman) and her son Toby (Christopher Gray) from her first marriage. At a rave with best friend Margo Masse (Alyssa Milano), Nicole meets David McCall (Mark Wahlberg), who is part of the same group of friends with Margo. Though he has borderline personality disorder and antisocial features, she is swept off her feet by his sweet, polite nature. When Steven meets David, he mistrusts him and does not believe in him when Nicole violates her curfews to spend more time with David. Eventually, while Steven and Laura are on a business trip, Nicole and David sleep together at her home, disobeying the house rule about unsupervised guests. One day, David scares Nicole by assaulting her friend Gary Rohmer (Todd Caldecott) upon seeing them hug each other. He shoves Nicole to the ground when she tries to stop him, giving her a black eye. Nicole ends things with David, leaving him crushed, but her father's now-intense opposition to David paradoxically drives her to accept David's apologies. Steven suspiciously checks into David's background and learns that David spent his early life with various foster families, until getting arrested or institutionalized. When David turned 18, he was released from foster care.Steven confronts David on a street corner and tells him to leave Nicole alone. However, David spins the encounter against Steven, making it look like Steven punched him, gaining the sympathy of Nicole who is driven further away from her father and deeper into David's arms. One evening, Nicole is invited by David to a party at his friend Logan (Tracy Fraim)'s house. She declines at first but, after a fight with her dad, reconsiders and drives over alone to surprise David. Looking in through a window, Nicole witnesses Margo smoking crack and having sex with Logan, only to be interrupted by David who takes Margo for himself. Nicole swears off David for good and leaves without anyone noticing her, then goes home and makes peace with Steven. The next day at school, David tries to surprise Nicole, only to be pushed away by her, and also by Gary. Nicole also ends her friendship with Margo, despite Margo saying that David took advantage of her while she was high against her will and her pleas for forgiveness. When David finds out why Nicole dumped him, he violently threatens Margo, unless she patches things up between him and Nicole. David becomes obsessed with Nicole, tattooing his own chest with the words "Nicole 4 Eva". He sees her hugging Gary again and gets furious. Nicole goes with Toby and Laura to the mall; they invite Gary along, but he has to get home. As Gary walks alone through the woods, David kills him by breaking his neck. David then vandalizes Steven's prized Mustang and leaves a taunting note: "Now I've popped both your cherries!". He then heads to the mall, where he harasses Nicole further, insisting that everybody is jealous of the love they had. Meanwhile, Steven breaks into David's house and finds an obscene shrine that David has built for Nicole, along with a box containing: a vandalized bracelet, which read "Daddy's Girl" but has been changed to "David's Girl"; a pair of Nicole's underwear; a defaced family photo, which finds Steven's head replaced with David's, and other objects. Steven angrily trashes the house. David returns home and promptly concludes that Steven has been there. He determines to break into the Walker residence, with the help of his four equally-violent housemates: Logan, Hacker (Gary Riley), Knobby (Jed Rees) and Terry (Jason Kristofer). A distraught Margo goes to Nicole's house and informs the Walkers that David has killed Gary.David and his gang behead Kaiser (Banner), the Walkers' German Shepherd. When Hacker tries breaking into the kitchen with an axe, Laura injures his hand with a drill. Knobby escorts Hacker to a hospital. Terry attempts to get inside from upstairs, but is thwarted by an umbrella-wielding Nicole. She then signals Larry O'Brien, the Walkers' private security guard, by flashing "SOS" with the light in her room. Larry arrives to confront David and Logan, and Steven comes outside to do the same. Terry shoots Larry dead from behind. The trio pummel Steven and take him hostage, then force their way into the house after taking Larry's handcuffs and pistol. They cuff Steven and Laura, taping their mouths shut. When Logan forces himself onto Nicole, Margo intervenes and is coldcocked. Toby escapes through another window, getting to Laura's SUV and using her car phone to dial 9-1-1, since David's gang cut the phone lines to the house. Toby has to start the engine to make the phone work; Terry notices this and shoots out the windshield, just missing Toby, who runs Terry down with the SUV. David brings a bound and gagged Steven into Nicole's room, so he can "give away" his daughter. He shoots Logan dead for trying to rape Nicole. Toby sees his mother's signal that she is handcuffed, retrieves the keys from the dead security guard, and frees both his parents. David gently tells Nicole, "It has to be this way", and asks her if she wants to go with him. However, Nicole agrees to it and pretends to reciprocate David's affection. Steven rushes David, but he hits him across the head with his pistol. Just as he is about to execute Steven with the gun, Nicole stabs David in the back with a "peace pipe" letter opener (which David himself won for Nicole at a carnival on one of their dates). David gets up and lumbers toward Nicole who stands ready for him despite being unsure of what he intends to do with her, but Steven gets up and pounces to disarm David from behind. Both men fight murderously until Steven tosses David through Nicole's bedroom window to his death on the rocks below. Margo and the Walkers share a group hug, and the police and EMTs have arrived by the morning.
Output: Question: Who is Nicole's father?, Answer: Steven