When the son of Robert and Katherine Thorn dies during childbirth, Robert is convinced to adopt a child and pass it off to his wife as their own in order to preserve her mental health. They name the child Damien and, very soon, mysterious events start to plague them. Animals, with the exception of large dogs congregating near the Thorn home, are terrified of the child, Damien violently resists entering a church and his nanny publicly hangs herself with a creepy smile on her face at his fifth birthday party. A priest, Father Brennan, tries to warn the Thorns that Damien may not be what he seems. Robert thinks Father Brennan is crazy, but a series of events, including the bizarre death of the priest himself makes Robert start to believe that his claims may have been true. A photographer named Keith gets embroiled in the situation, showing Robert photographs that seemed to predict the bizarre deaths that had been occurring. Robert and Keith travel to Amsterdam and Israel to investigate Damien. They learn that he is the Antichrist and find that the only way to kill him is with some mystical daggers. When Keith goes to retrieve the daggers after they were discarded by Robert, who was appalled at the idea of killing a child, a pane of glass mysterious slides off a boat, decapitating him.