After his father's death, high school student Kale Brecht (Shia LaBeouf) becomes sullen, withdrawn, and depressed—so much so that, after a wild outburst at school, he is placed under supervision. The order includes house arrest. His mother, Julie (Carrie-Anne Moss), works day and night to make ends meet, but receives only indifference and lethargy from him. While staying home, he begins to suspect his neighbor: it's increasingly likely he's a serial killer. But are these suspicions merely the product of a growing claustrophobia?