After performing an open heart surgery, Steven Murphy, a cardiothoracic surgeon in Cincinnati, meets 16-year-old Martin Lang, whose father died a few years earlier, in a diner. Steven goes home to his wife Anna and their children Kim and Bob. Steven invites Martin to meet his family, and Martin gets along with everyone, especially Kim. That night, Martin invites Steven to his house for dinner the next day.
At Martin’s house, after dinner, Martin goes to bed, leaving Steven alone with his mother. Martin’s mother begins flirting with Steven, and he leaves.
Martin visits Steven’s office, complaining of chest pain, but tests show nothing wrong. Martin invites Steven over again, saying his mother finds Steven attractive, but Steven refuses. Afterward, Martin’s demands for Steven’s attention grow increasingly frequent and desperate. Steven is troubled to learn that Martin gave Kim a ride home on his motorcycle.
One morning, Steven’s son Bob is unable to move his legs, so Steven and Anna rush him to the hospital, where numerous tests are performed. Martin tells Steven that, to “balance things” for his father, who died while Steven was operating on him, Steven must kill a member of his own family. Otherwise, within a few days, Steven’s family will all die from paralysis, an inability to eat, and bleeding from the eyes. Steven has Martin escorted from the hospital. Later, Bob begins refusing to eat, but no cause can be found.
