Adam (Jake Gyllenhaal) is an associate professor of history at a university. He lives with his girlfriend, goes to get off work and comes home from work every day, and leads a quiet life. Until one day, he found an actor who looked exactly like him in a movie. He used the Internet to find the actor's information and contacted him. The actor who looked exactly like Adam was called Anthony, who had a pregnant wife. At first, he only regarded Adam as a crazy fan, until he searched Adam's information on the Internet and finally made up his mind to meet Adam. The two agreed to meet in a hotel. Adam saw Anthony who looked exactly like him, and he was terrified. He told the other party not to see him again and left in a hurry. However, a few days later, Anthony showed up at Adam's house and made a strange request...