In 1985, 16-year-old high school student Ted Stroehmann is about to go on a prom date with his dream girl Mary Jensen when he gets his scrotum stuck in his zipper. He is hospitalized after managing to painfully unzip it, which causes him to miss their date. Ted subsequently loses contact with Mary.
Thirteen years later, 29-year-old Ted is still in love with Mary. On the advice of his best friend Dom, Ted hires private investigator Pat Healy to track her down. Healy discovers that she is an orthopedic surgeon living in Miami. After observing her for a few days, Healy becomes fixated on her. He returns to Providence and lies to Ted about Mary, telling him she is overweight and has four kids by three different men. Healy quits his job and returns to Miami to pursue her. He resorts to lying, manipulation, and stalking to win Mary over.
Healy and Mary spend several weeks dating before her friend Tucker exposes Healy as a fraud. Tucker tells Mary that Healy is a suspected serial murderer. An enraged Healy follows Tucker and discovers him to be a fraud himself, who is also infatuated with Mary. Years earlier, Norm intentionally injured himself in order to get close to Mary, hoping she would take him on as a patient. He pretends to still be disabled in order to gain Mary's sympathy, and uses his friendship with her to drive away other suitors.
Meanwhile, Ted finds out that Healy was lying about Mary and drives to Florida to see her. During the drive, Ted picks up a hitchhiker who leaves a dead body in Ted's car. Ted is mistakenly arrested for the murder and bailed out by Dom after the police catch the real killer. Ted finds Mary and they begin dating. Things go well until an anonymous letter reveals that Ted hired Healy to find her, causing Mary to get upset and dump Ted. Ted then tracks down and confronts Healy and Norm, who deny sending the letter. Things come to a head when Dom, who is Mary's ex-boyfriend "Woogie", attacks her in her apartment. Mary previously had a restraining order against Dom after he became obsessed with her, which started again when Ted found her.
Ted, Norm, and Pat intervene and save Mary from Dom. Ted realizes that the only one who did not resort to lying or manipulation to win her over was her ex-boyfriend Brett Favre, whom Norm had lied to Mary about to get rid of him. After reuniting Brett with Mary, Ted leaves and Mary chases him down outside. She confesses that she loves Ted and wants to be with him, and they kiss.
Ben Stiller as Ted Stroehmann,
Cameron Diaz as Mary Jensen,
Matt Dillon as Pat Healy,
Chris Elliott as Dom "Woogie" Woganowski,
Lee Evans as Tucker/Norm Phipps,
Lin Shaye as Magda,
Jeffrey Tambor as Sully,
Markie Post as Sheila Jensen,
Keith David as Charlie,
W. Earl Brown as Warren Jensen,
Sarah Silverman as Brenda,
Khandi Alexander as Joanie,
Willie Garson as Dr. Zit Face
Harland Williams as The Hitchhiker,
Richard Tyson as Detective Krevoy.
Rob Moran as Detective Stabler.
Jonathan Richman as The Singing Narrator.
Steve Sweeney as Policeman.
Lenny Clarke as Fireman.
Richard Jenkins as Ted's Psychiatrist.
Brett Favre as himself