American Ambassador Robert Thorn (Gregory Peck) passes another child off as their own to wife Katherine (Lee Remick) when she gives birth to a stillborn son, little realizing that the child is the son of Satan. Life in England remains normal for a few years until the child, Damien (Harvey Stephens), becomes a toddler and strange deaths start occurring. Katherine falls from the staircase. the nanny hangs herself and a priest is speared to death in an accident. It turns out that whoever stands in the way of Damien must be rid off. As the truth unfolds, Robert learns that Damien is the Anti-Christ, who have come to take over the world and can be killed only with the seven daggers of Meggado.