Drew (Ben Afflek) is wowing a bunch of ad execs with a promotional idea for spiked eggnog. That night with his girlfriend he presents her with two tickets to Fiji. She's disappointed because she was expecting a proposal & walks out on him. The next day, he's at work and tells his secretary to send her a gift to win her back. Drew realizes that he's going to be alone for Christmas, so he starts calling up all the people in his address book. No one wants to have him over for Christmas. He ends up running to the airport to catch the shrink of his girlfriend when he's trying to leave on a plane with his family. The shrink tells him to write down his grievances on a piece of paper, and then burn them at a place that reminds him of his childhood.Drew drives out to the suburbs and pulls up to the house he grew up in, which is now occupied by a different family. Inside the house, the parents Mr. Valco and Mrs. Valco (James Gandolfini and Catherine O'Hara) are arguing about the son spending too much time on the computer. They see Drew kneeling down on the sidewalk and light something on fire. The dad walks out and hits him over the head with a shovel.Inside the house. The family is standing around wondering if he's dead. When Drew comes to, the Valco's let him stay for dinner. They ask him to leave. Drew offers to pay them $250,000 to pretend to be his family for the holidays. A lawyer comes and they sign legal papers. He makes them go tree shopping, and the dad has to wear a Santa hat. The sister Alicia (Christina Applegate) comes home and has no intention of adopting this new brother. She demands that they kick him out.At dinner, Drew shows up with an old man and says that he is the Grandpa. He's a local theater performer who Drew hired to fill the role. They all sit down and have dinner. Drew pulls out a script and gives copies to everyone and asks that they all read through the scene. Everyone gets annoyed. Mr. Valco tells Drew that he and his wife are thinking about separating and having him there is making things worse. Drew tells him to go out and buy something for himself that will make him feel better. Then he tells the wife that he's going to set up a private photo shoot and have her all dressed up. She's so happy she cried. At the shoot, she's dressed in leather and a ton of makeup. She seems to be having a great time.Drew gets the son and sister to go sledding with him. The old hill is now too small, so he charters a helicopter and carries them to the top of a mountain. They sort of dare each other into getting on the sled. Then they go screaming down the mountain. At the end Drew and Alicia crash and start laughing. Drew & Alicia both get colds and spend the afternoon talking and watching TV. She tells him about a time when she was 9 and saw a tree covered in ice & wanted to live that moment again.Drew confides that he never lived in that house. His father walked out on them when he was little. His mother worked in a diner, and he spent every Christmas alone. Alicia & Drew almost kiss, but she sneezes. Later on, Drew takes Alicia outside. He had the tree covered in ice and flew in a bunch of dancers and singers. Alicia gets offended because it's so over the top. Meanwhile, the girlfriend is talking with her own parents. She got the gift (a diamond bracelet) that his secretary sent her, and she wants to make up. She calls and says that she wants to meet his family.Drew had just told the family that he was leaving. But now he is forced to offer more money to have them pretend to be his family in front of his girlfriend, and her parents. The old man playing Grandpa couldn't show up, so his understudy comes over. Alicia comes home and apologizes to Drew. She kisses him. As soon as she leaves, his (ex) girlfriend walks in and they end up kissing too. Alicia sees him. Alicia decides to get even. She plays along with the family, making cutting remarks and finally causes Drew to lose it. He rants about how they were just making out in the kitchen. Then he tried to cover by saying they're a very affectionate family.Meanwhile the son is upstairs. "Grandpa" had come in while he was looking at porn and they found a website that was posting the pictures that Mrs. Valco had gotten taken. She didn't know they were being posted in that way, of course, but the son is frozen in shock. The whole family (girlfriend and her parents included) come walking in and see the screen. Everyone freaks out. The parents of the girlfriend finally say that they've seen enough, and they all storm out. Then Mr. Valco storms out saying he's staying at a hotel.Drew goes back home to his huge empty apartment. Mr. Valco shows up. Drew stills owes them money. Drew writes a check and then they talk about how Mr. Valco wishes that he didn't separate from his wife. Drew mentions that he still has the ticket to the performance of Scrooge ("Grandpa" had given the entire family tickets to his performance as Mr. Scrooge earlier on). They go, not knowing if his family will be there. They are. Mr. Valco and Mrs. Valco make up.Drew hooks the brother up with a cute girl in the audience. When he goes outside, he finds Alicia. They kiss and make up. The ex and her parents drive by and witness it, in all its open-mouthed glory.