The seven knives of Megiddo, the only weapons capable of killing the Antichrist, are discovered in a Chicago, Illinois, construction site. The knives are sent to De Carlo, a priest at a monastery in Subiaco, Italy, who is aware that businessman Damien Thorn is the Antichrist. According to ancient prophesies, the “Beast” will soon complete his seven year reign and Christ will be reborn in England for the final battle between good and evil. Meanwhile, Damien, who has run his company, Thorn, for seven years, prepares for the Second Coming of Christ, vowing that the “Nazarene” will be destroyed. Damien confides to his private secretary, Harvey Dean, that he will soon be appointed ambassador to Great Britain. In England, a Rottweiler dog barks at the sitting ambassador, who then returns to his office in a trance and commits suicide in front of journalists, including television reporter Kate Reynolds. When Damien is offered the ambassador’s post, he negotiates to become president of the United Nations (UN) Youth Council. Elsewhere, an astronomer discovers that an unusual alignment of stars will occur on 14 March 1982. He informs De Carlo of the celestial “trinity alignment,” heralding the birth of Christ. De Carlo assembles his cabal of monks, then arms the men with Megiddo daggers and they travel to England to kill Damien and protect the Christ child. Meanwhile, Kate meets Damien at a party and he accepts her invitation to appear on her television show. In return, Damien asks Kate and her son, Peter, to join him at the park on Sunday. There, De Carlo’s monks observe Damien and later decide to target him during his appearance on Kate’s show. A monk sneaks onto a rickety catwalk above the stage, but as he prepares to strike, he trips on a rope and falls. As he swings into a plastic tarp, he knocks a stage light into hazardous material that ignites in flames. Damien sees the Megiddo dagger and is determined to find the other six knives. After the show, Dean learns his wife, Barbara, has gone into labor. Later, De Carlo, the monks, and astronomers watch as a bright light heralds the convergence of the three stars. The next morning, Damien notices one of De Carlo’s monks watching him from the street. Damien realizes it is a trap, but follows the monk to the ruins of a remote church. Knowing Damien is behind him, the monk alerts two companions on a walkie-talkie. The monks throw a coat over the head of a man they believe to be Damien and stab him with their daggers, only to discover that they have mistakenly killed their fellow monk. Lightning strikes and the snarl of a vicious Rottweiler send the monks scurrying into an underground tunnel to escape. However, they find the tunnel bricked up and a heavy grate drops overhead, trapping them. Damien decides that the only way to kill the Nazarene is to murder every male child in England born between midnight and six a.m. on 24 March. He orders Dean to call a meeting for Sunday after the fox hunt and also inquires about Dean’s newborn son, but the secretary claims his child was born 23 March. On Sunday, Kate watches her son ride in his first hunt and Peter is excited about being “blooded” with the fox’s blood as part of the ritual for a first time participant. When Damien takes a substantial lead in the hunt, a monk shoots the fox, releases a decoy fox, and hides as Damien and his dogs follow the animal. Once Damien passes, the monk drags the dead fox in another direction, misleading the other dogs and hunters. As Damien’s dogs kill the decoy fox, the monks trap Damien on a narrow bridge. However, Damien spooks one monk’s horse and the man is tossed over the bridge to his death. Damien’s dogs rip the other monk to shreds. Damien dips his ascot in the monk’s blood, then returns to the manor, where he “bloods” Peter. That night, Damien orders his “disciples of the watch” to slay the 24 March male babies. His congregants, including priests, nurses, boy scouts, and many other children, start the killing spree and, days later, Kate reports on the mysterious infant deaths. That night, De Carlo tells Kate that the dead babies share a common birthday, which marks the second coming of Christ, and Damien is the Antichrist. Kate does not believe De Carlo, but he leaves her with the babies’ birth certificates and his research on Damien, which reveals that he has a birthmark in the shape of “666” under his hair. Peter eavesdrops on their conversation, then telephones Damien, who asks the boy to follow the priest. The next day, Peter shadows De Carlo throughout London and sees him visit Barbara Dean. When Dean arrives home, Barbara warns him to stay away from their son. Meanwhile, Damien and Kate stroll around his estate and she falls into the river. After a moment’s hesitation, Damien rescues her. Later, they make love, but he turns violent and leaves her bruised and scratched. The next morning, Kate awakens alone, then discovers Damien sleeping on the floor in another room. Seeing the “666” birthmark, Kate sneaks away, not realizing Damien is awake. Later, Damien and Peter confront Dean, demanding to know why De Carlo visited his wife. Damien claims there is only one infant left and Dean must kill his own son but Dean insists they are crazy and leaves. Meanwhile, Barbara irons while watching over her son. A Rottweiler barks at the window and she has a vision of her son in ashes. In a trance, Barbara picks up the steaming iron and walks toward the baby. Moments later, Dean returns home. As he walks to his son, he moans in horror, and Barbara murders her husband with a hot iron slammed into his eyeball. Meanwhile, De Carlo arrives at Kate’s studio to inform her that the Holy Child is safe, but warns that her son is with the Antichrist. To save Peter, she must lure Damien to the abandoned church, where De Carlo will kill him. Kate rushes to Damien’s estate and offers to lead Damien to the Christ child in exchange for her son. Damien insists that Peter join them and, when De Carlo attacks, Damien uses Peter as a shield and the boy is killed. Damien strangles De Carlo, then wanders the ruins calling for Christ to show himself. Kate rushes up behind him and stabs Damien with the Megiddo dagger she pulled from her son’s body. A bright light shines and Christ, “not as a child, but as the King of Kings,” hovers above them. Damien shouts that Christ has won nothing, then dies. A figure carries Peter toward Kate and she embraces her son, who may yet live, fulfilling Revelation’s prophecy.