American diplomat Robert (Gregory Peck) adopts Damien (Harvey Stephens) when his wife, Katherine (Lee Remick), delivers a stillborn child. After Damien's first nanny hangs herself, Father Brennan (Patrick Troughton) warns Robert that Damien will kill Katherine's unborn child. Shortly thereafter, Brennan dies and Katherine miscarries when Damien pushes her off a balcony. As more people around Damien die, Robert investigates Damien's background and realizes his adopted son may be the Antichrist.