Synopsis The film opens (and ends) at the wedding of Elliot Sherman and Caroline Swann. Elliot explains, through voice-over narration, that while most romantic comedies are about two people who were always meant to fall in love and live happily together forever, this movie is different. It is about the guy who is nice and well-meaning, but not the person the girl is supposed to be with. His grandmother had a word for that person: the Baxter, and Elliot is a classic example of a Baxter.
The movie then flashes back to the beginning of Elliot's relationship with Caroline Swann, meeting her first as her accountant. At the same time, he meets a temp-worker filling in for his sick secretary named Cecil Mills that he has much in common with, including a love of reading the dictionary.
Caroline and Elliot quickly fall for each other and begin a serious, if dispassionate, romantic relationship, with Elliot eventually proposing. While visiting her family over the holidays, he learns about her ex-boyfriend from high school, Bradley. Soon after, Elliot and Caroline run into Bradley and his girlfriend at a bar. While Caroline swears that there is nothing between her and Bradley, Eliot senses a chemistry between them and begins to worry about the future of his relationship.
Nervous, Elliot runs into Cecil again in an elevator ride at the office he works. She can tell he is upset about something, at which point he admits that he's positive his fiancée is about to leave him. He explains to Cecil that he has a history of being well-intentioned but timid in relationships, always losing his girl to more handsome and confident men, complaining about how he's destined to be a lonely Baxter. One example he gives includes when, at prom, he didn't dance with his date (who, to be fair, was on crutches), only for her ex-boyfriend to show up and steal the last dance with her while he was getting them another round of drinks. Cecil begins to give her perspective of Elliot's problem, when she realizes she's on her floor. In a hurry to get to her new temp-job, she gives Elliot an address to meet her at so they can finish their conversation.
Elliot initially hesitates but eventually decides to go the address Cecil gave her, largely to hear what advice she had to give. When he arrives, he learns the Cecil is a singer, though her crippling stage fright worsens her performances. After her performance, Cecil and Elliot share several drinks. Eventually Cecil tells Elliot what her advice is: that Elliot needs to be more impulsive and romantic. Elliot reacts uncertain, but admits she might have a point. They exchange numbers, and agree to call each other at any time if they need anything.
Hours later, Cecil calls Elliot in tears, telling him that she and her boyfriend Dan had a fight and that she needs somewhere else to sleep that night. Elliot agrees for her to come to his house, folding out his futon and offering her a pair of his pajamas.
The next morning, Caroline and their wedding planner show up at Elliot's apartment to discuss the future wedding. Unprepared and anxious that Caroline will see Cecil and get the wrong idea, Elliot starts to make wild and uncharacteristic suggestions for their wedding. Upset and confused, Caroline breaks down in tears and says that she doesn't think she can marry Elliot after all.
Depressed and convinced he’s blown another chance at eternal happiness, Elliot considers suicide. At the last moment, Caroline’s brother-in-law talks him out of it, telling him that Caroline will give him one more chance, but he has to be romantic. With this in mind, Elliot buys flowers and candy before showing up at Caroline’s apartment to make up. He discovers, however, that Bradley is living there as well after recently breaking up with his girlfriend. The three go out on an awkward date, where Eliot tries to be romantic but ends up mostly showing how timid he is. Eventually he stands up for himself, saying that he is trying his hardest to be a good boyfriend to Caroline, but that he isn’t perfect. After the dinner, the three go out dancing, where Caroline starts to pay more attention to Elliot than Bradley. Bradley reveals that he is leaving the next morning, expecting Caroline to say she is going with him. When she seems happy to let him go, Elliot feels pretty good about his chances of actually being married.
The week before his wedding, Elliot tells Cecil about the events of the date night with Bradley. Cecil is supportive of Elliot’s wedding, though clearly upset, and tells him that she is moving to Cleveland with her boyfriend Dan. As the wedding gets closer, Elliot starts to question if he truly loves Caroline or just wants to be finally married. On the day of his wedding (the same wedding as at the beginning of the movie), the ceremony is interrupted by Bradley bursting in and confessing his love for Caroline. The two embrace and kiss, much to the delight of the attendants of the wedding (including Elliot’s own parents). But Elliot reminds that this isn’t their story, but his. Hurrying across town, he catches Cecil just in time for them to kiss.
The credits are interrupted by a short scene, told from the perspective of Dan. From his perspective, Elliot is the romantic lead, and he is the Baxter.