In Boston, Jenna is assistant to Mia at Trend Fashion, a successful magazine on the fourth floor of a tall building. She is so good at her job that Mia credits her for the business doing so well. Jenna also wants to be a fashion designer and she is very good, but she is reluctant to tell Mia this.Jenna's mother will be out of the country for Christmas and they won't be able to spend the holiday together. But her father who has remarried wants her to come spend the holiday with him and his new family, and he arranges for airplane tickets.Jenna's neighbor Sebastian comes over with food and they talk. He is having trouble in his relationship with Abby.Helmut is taking photos of a model in a sexy Mrs. Santa suit in front of a Christmas tree, and Jenna is helping. However, there is a delay in getting everything needed to finish. The model has left but Jenna is pretty enough to take her place in the Mrs. Santa suit.Mia, who hates Christmas and won't allow decorations in the office, is experiencing anxiety over a visit from her brother Cooper, who owns half the business but has never done any work and takes advantage of his wealth by going out with numerous beautiful women. Cooper arrives at Mia's building with the gorgeous, nasty and shallow Brittany, his latest. Cooper visits his sister alone. Then he gets on the elevator, which has traditional carolers. Before he arrives at his destination, Jenna gets on the elevator wearing her Mrs. Santa outfit, and Cooper tries unsuccessfully to hit on her. Cooper persuades the annoying carolers to go sing for someone who really needs cheering up, and Cooper and Jenna are alone on the elevator with mistletoe, and the elevator gets stuck. Cooper can't resist kissing Jenna and Jenna isn't exactly resisting, but she does indicate she didn't care for that. When they exit the elevator, Brittany is there and she comments about the "bimbo model".Cooper and Brittany go to the bar where Sebastian works.While decorating her apartment, Jenna tells Sebastian about her experience in the elevator but Sebastian's main interest is how Jenna looks in the photos.The next day Mia asks Jenna to go to where her brother is staying and pick him up. Cooper is not wearing a shirt, and he is happy to see the girl from the elevator. He asks Jenna to go to breakfast with him, but Jenna says she has to go back to work. Cooper says he owns half the company so Jenna has to do what he says, and she agrees. They talk about their lives. Cooper says he and Mia grew up with parents who didn't divorce but treated their relationship like a business arrangement and did what was prudent rather than caring about their family. At least he and Mia got their work ethic from their parents. Jenna feels like her father rejected her and only cares about his new family.Back at the office, Cooper wants a place to work because he's interested in actually contributing. Mia thinks he just wants to be close to Jenna and warns him to stay away from her, but he doesn't listen and there is enough space in Jenna's office that they can share. Asked to give him a tour, Jenna hands him off to Audrey the receptionist. Cooper sees several old friends including Helmut, who is very happy to see him.Jenna gets a call from her father who says she will need to shop for Ruth, his new wife, and her children, and he will send a list of presents they might like. Jenna agrees but resents having to do this for people she hardly knows who won't accept her. Jenna also gets a call from Sebastian, who she pretends is her boyfriend, so Cooper will stop trying to hit on her. Nevertheless, Cooper is smitten and continues his efforts to woo her. He believes he needs to change his life and stop dating numerous women.Brittany visits Cooper at work and discovers the "bimbo model" is not a model and makes a condescending comment.Helmut delivers the photos of the sexy Mrs. Santa for Jenna to go through. Cooper takes one for himself.As Sebastian helps Jenna shop, he sees Cooper and recognizes him as one of his customers. Jenna continues to pretend Sebastian is her boyfriend, and he enjoys doing this. They all end up at the apartment where he is staying and have a good time decorating.Then Jenna's life falls apart. First she shows Mia her designs and Mia acts like Jenna is wasting her time doing something so foolish. Jenna throws the samples in her trash. Then she gets a call from her father who says Ruth's family is coming and they won't have room for her. Jenna cries.Cooper takes the designs out of the wastebasket and asks Mia about them. Mia says she can't lose such a good assistant and chastises her brother once again about treating Jenna like one of his conquests. Cooper later takes the designs to Helmut, who is impressed. Cooper asks Helmut to have the dresses made.Cooper and Brittany go on a date but Sebastian is not working that night. And he is getting tired of Brittany and says he can't be like he was. Brittany is angry and says he'll come back to her like he always does.Cooper wants a holiday party and he wants Jenna to plan it. They will have to persuade Mia, who acts like a Scrooge about Christmas. It will take place off the premises.Cooper asks Jenna to come in on a Sunday, claiming it is work-related. Jenna finds rose petals on the floor in the hall and poinsettias in the office. Cooper just wants a romantic encounter. At first Jenna is willing and they kiss again. Eventually, something goes wrong and Jenna walks out angry, thinking Cooper is just treating her as a novelty. She doesn't understand that Cooper really wants to change and to commit.Brittany goes to Cooper's place when he is too sleepy to do anything. While he is asleep, she discovers the photo of Jenna in his jacket. Brittany makes herself look sexy, unbuttons Cooper's shirt, and takes a selfie, sending it to Jenna. Sebastian sees what she did but suspects something is fishy.Nevertheless, Brittany and Cooper are together another night at Sebastian's bar. Sebastian confronts them and Cooper is shocked and leaves. Brittany complains to management and Sebastian is fired.Cooper arranges for Jenna's designs to be displayed at the holiday party. When he goes back to the bar he asks about Sebastian and is told he was the one that got Sebastian fired. He is shocked at what Brittany did and gets Sebastian rehired.Jenna goes to the party and is so happy to see her designs, and her father. Cooper arranged for him to be there.Cooper also proposes to Jenna, and she says yes.Sebastian reunites with Abby.Mia gets on the elevator in her building with a good looking man.