After leaving a party at a women's dormitory (aka the "virgin vault"), Matthew (Jonathan Tucker) is trapped in an elevator with an unknown, and unseen, woman when the power goes out. Matthew and this unknown woman have sex in the dark. When Matthew wakes up in the morning—still in the elevator—he finds himself alone with a pair of her panties.
On a mission to find his mystery maiden by finding a matching bra for the panties, Matthew becomes the maintenance man of the virgin vault. After releasing mice, he goes room to room, setting traps. He convinces the panicked women to leave their rooms and then starts to look for a match. When he is unsuccessful, he continues to break things (such as the air conditioning) in an effort to find his woman. He also fixes the television set, which is greatly received by women he refers to as "Jane-ites", as they have a great interest in films adapted from books by Jane Austen. He doesn't get much help from his roommate Rod (James DeBello), who keeps telling him to give up, and together they philosophize about men and women. Rod tells him that he doesn't need a girlfriend and that it's futile to try to find the "bra matching the panties", and Matthew accuses him of being too macho. Rod introduces Matthew to the "penile power", which involves the use of weights attached to his penis as a means of increasing the organ's size. He does this and insults women to make himself feel better about the problem he has with his manhood; he suffers from hypospadias.
Early on, Matthew watches as a woman named Patty (Emmanuelle Chriqui) and her boyfriend Crick (Johnny Green) fight. Crick is the epitome of the macho man stereotype, with his big pectorals, conceited attitude, and abusiveness. He wears a ponytail, a manicured goatee, "male make-up", and chews nicotine gum, much to Matthew's dismay. Matthew tries to save Patty, but is hurt by Crick. Crick leaves, and Patty tries to help Matthew, but Matthew can't help but think of Patty's reputation as a "slut."
While searching one room, Matthew finds himself trapped in the bathroom when the occupant returns. Matthew is attacked by Wendy (Larisa Oleynik), until she recognizes him as a high school classmate. Wendy decides to help Matthew in his quest to find his mystery maiden, hoping that, in the process, she may find one of her own, as she is a closeted lesbian.
Matthew is nervous about talking to girls. Arlene (Katherine Heigl) and his teacher Ms. Stern (Aimee Graham) disparage Matthew, asserting that women are more dominant than men are. Arlene beats him at foosball. Ms. Stern asserts that women, rather than men, should be in command. Rod tells Matthew that he's a chicken and should just give up on girls, while Matthew tells him that he has never been able to speak to girls, especially Cynthia (Jaime Pressly).
Matthew puts an advertisement in the school newspaper asking the girl he's seeking to meet him in the basement on a Thursday night. He sits in the dark every Thursday night, waiting for her to show up. The door opens one night, and he thinks it's her, but it's Wendy, coming to check up on him. Finally, the mystery maiden does show up, only to tell him to stop looking for her.
Despite the approach of the end of the semester, Matthew isn't deterred. He disguises himself in drag, as Francesca, as a means to continue his search. In drag, he is actually able to talk to Cynthia one on one which, (until she is injured later on), he is not able to do because he is intimidated by her good looks. Rod flirts with Francesca and later brags to Matthew that he had sex with Francesca. This makes Matthew so angry that he adds another weight onto Rod's "penile power" device, hurting him. Crick makes a pass at Matthew in drag while he fights with Patty. Matthew bites off part of Crick's tongue. As a result, Crick is unable to speak without lisping.
Desperation sets in, so Matthew appeals to his mystery maiden by proclaiming his love for her to the whole dormitory. He finally determines his mystery maiden is Patty. She initially rejects him because she thought that he would see her only as a slut. Crick sees that Matthew wants Patty, but Matthew has him arrested for sexually assaulting him (when he was dressed as Francesca).
Matthew introduces Rod and Dora, and Arlene and Wendy hook up. Cynthia shows off her newly found martial art abilities, and Ms. Stern learns a valuable lesson on gender equality, as Matthew stands up to her in front of the class, to an ovation. Finally, Matthew proclaims his passionate love to Patty, who sees his loving eyes, and they kiss.