Owen Matthews arrives at Westlake Preparatory Academy. That night Owen's roommate, Tom, tells him they are sneaking out. A group of students consisting of Graham, Mercedes, Lewis, Randall, Regina, Tom, Dodger and Owen play a game called Cry Wolf, where someone is marked as a "wolf" and the group tries to figure out who it is.
After meeting his new journalism teacher, Mr. Walker, Owen and Tom meet everyone for lunch. They discuss the police finding a girl's body, Becky, after it was dragged through the woods by a wolf. The group considers who could have murdered Becky, when Dodger proposes expanding Cry Wolf to the entire school. Owen suggests creating a fake e-mail telling everyone about a serial killer who goes from campus to campus killing students. They describe the killer as wearing an orange ski mask, a camouflage jacket and brandishing a hunting knife. That night, they send out the e-mail.
The next day, the entire school has spread the story in the e-mail. Owen receives an instant message from someone using the name "Wolf". Tom and Owen accuse Dodger, but she claims she was studying with Regina.
Tom and Owen find their dorm room trashed. When the instant messenger comes up on Owen's laptop, they find a piercing stud and blood on Owen's keyboard. Tom blames Regina, who has a recipe for fake blood. When accused, she insists she was on a field trip.
Believing Dodger is lying, Owen confronts her. Dodger informs him that she was visiting her mother. Deciding that Randall is behind the odd behavior, Owen tries tracking him down, to no avail. Owen once again seeks out Dodger, and finds her kissing Mr. Walker.
In his journalism class the next day, when Owen reaches into his bag for supplies, a hunting knife falls out. Mr. Walker escorts Owen to the Headmistress's office. Owen tells Mr. Walker that he knows about his relationship with Dodger, and that he will tell the headmistress if Walker reveals the knife. Mr. Walker agrees not to say anything.
On the night of Halloween, "Wolf" attacks Owen. Thinking Tom was trying to prank him, Owen goes to leave with Tom's car, but sees Wolf behind him. The attacker ends up being Mercedes, who was trying to prove that attackers can be women.
The following day, Owen and Mercedes meet with the headmistress, who decides that Owen's fate will be decided over the weekend. The rest of the group is forced to stay at school over the weekend. Owen contacts them to meet in the chapel. Owen, Dodger, Tom, Lewis and Regina meet and try to get to the bottom of the attacks. While Lewis is on the phone, Mercedes is apparently attacked in the bathroom by Wolf. Owen unsuccessfully tries to call for help.
The rest of the group finds Randall's body in a confessional. After the group scatters, Owen runs to the parking lot to see that Mr. Walker is still on campus. Owen runs to Mr. Walker's office as his phone starts ringing. Owen answers to Dodger crying on the other end; she has found Mercedes dead. Dodger tells Owen she is coming and can see him through the window. He looks out to see Wolf kill her. Suddenly Mr. Walker enters the room. After noticing that Mr. Walker has a jacket, an orange mask and a knife, Owen shoots him. The door is suddenly opened by Dodger, Tom and Regina.
Owen is arrested for murder. The group admits that it was a prank to get Mercedes and Owen back for making them stay on campus. It is discovered that Mr. Walker was involved with Becky, the gun in his desk being the same one that killed her. Dodger visits Owen, and says that she would never have played the game if she knew that Mr. Walker was cheating on her, revealing she had organized everything. She had killed Becky because she was jealous of Mr. Walker's relationship with her. She had set up the game, knowing that Owen would blame Mr. Walker for the killings, thereby killing him and making her happy. Owen threatens to report her, to which she replies that no one would believe him.
America Online also helped publicizing the film in July/August 2005; launching an alternate reality game for AIM users to play by sending instant messages to each other, which ran for the duration of the film's promotion. The game itself ran similarly to the popular game 'Mafia'; just replacing townspeople and mafia with sheep and wolves. The film was released theatrically in the United States on September 16, 2005. At the box office, Cry Wolf grossed $10 million in the US and $5.5 million internationally, making a worldwide total of $15.6 million.
Film review aggregator Rotten Tomatoes reported an approval rating of 22% based on 45 reviews and a rating average of 3.9/10. The website Metacritic gave the film a weighted average score of 39 out of 100 based on 14 critics, indicating "generally unfavorable reviews".