Adam is a student at Mercy College, a fictitious Midwestern college, as an English Literature major, who wants more in his dull life than classes and studying. One day by chance, Adam meets Evelyn, an attractive graduate art student, at the local museum where he works. Afterwards, his life takes an unexpected turn. Never having had success with women, the nerd-like, socially awkward Adam is flattered when Evelyn shows an interest in him and, at Evelyn's suggestion, begins a regular exercise regimen, eats healthier foods, and purchases contact lenses in place of his eyeglasses. These initial changes in Adam's physical appearance are well received by Adam's friend Phillip and his girlfriend Jenny. Later however, Evelyn cajoles Adam into undergoing plastic surgery and succeeds in persuading him to cut himself off from Phillip and Jenny as well as all his old friends because Evelyn claims to Adam that SHE is his one and only friend. After another while, Adam proposes marriage to Evelyn, and right away, she accepts.
But at the climax, Adam learns that he has been part of Evelyn's MFA thesis project, a topic often touched on in conversation throughout the movie but never fully explained. Evelyn relates that she had been instructed to "change the world" by her graduate adviser, but that she has chosen to change "someone's world", her academic work ultimately consisting of "sculpting" Adam into a more attractive human being. Her true nature and cruelness becomes known one day when she presents Adam before an audience of students and faculty as her "creation", which somewhat embarrasses him. Accordingly, none of the feelings she has shown him this whole time are genuine; at no stage in their "relationship" did she ever fall in love with him; her videotaping of their lovemaking is just a part of the project's documentation. The next day at her gallery opening, Evelyn announces before the live audience that she is not going to marry Adam and the engagement ring he offers her is simply one of the exhibits of her art installation, albeit the "capper to my time at Clarkson."
Publicly humiliated and devastated, Adam confronts Evelyn, demanding an explanation for her actions. Completely unapologetic, Evelyn responds by saying that he should in fact be grateful to her, claiming that, objectively speaking, she has been a positive influence on his life, making him a more attractive and interesting person in the eyes of society. Finally seeing the devious vixen that Evelyn really is, Adam tells her that they are finished. Evelyn cynically states to Adam that there never was a "relationship" between them to finish in the first place.
In the final moments of the film, the beaten and emotionally broken Adam stands alone, surrounded by the remnants of his life before Evelyn. Even Adam's old friends, Philip and Jenny, treat him with scorn and refuse to forgive him for dropping them in favor of Evelyn. Moving to a camcorder, he watches a section of a tape recorded earlier in the film, a moment in which Evelyn had whispered in his ear what she described as the one "true" thing of their relationship. The film ends as Adam watches and continuously rewinds the tape, listening to Evelyn's truth over and over again.