Rome is shattered by a series of gruesome murders that paint the Eternal City deep red. The suspicion grows that these atrocious crimes are connected with the return of one of the most heinous serial killers of our time - Karl the Butcher.

David O'Hara is a troubled medical student who kidnaps, rapes and murders women. He impregnates one of his victims, Melissa Daniels, in an attempt to replace the family that he lost as a young boy. However, the police rescue Melissa from David's warehouse, and David goes on a murderous rampage to get his family back.

It starts off in Vietnam where John Saxon gets bitten by P.O.W. John Morghen who has been infected with some sort of cannibal virus. A few decades later in Atlanta, Georgia, Saxon wakes up from a nightmare flashback of what actually happened back in 'Nam. Saxon then receives a call from Morghen asking him if he wants to go out for a drink but Saxon refuses remembering the incident in 'Nam. Morghen has turned into a cannibal and is soon on the run after biting into a woman's neck. He barricades himself in a department store and shoots some folks with a shotgun. The cannibal virus spreads and soon Saxon joins veterans Morghen and Tony King along with some others to wreak some havoc.

In the small New England town of Dunwich, a priest commits suicide by hanging himself in the church cemetery which somehow opens the gates of hell allowing the dead to rise. Peter, a New York City reporter, teams up with a young psychic, named Mary, to travel to the town where they team up with another couple, psychiatrist Jerry and patient Sandra, to find a way to close the gates before All Saints Day or the dead all over the world will rise up and kill the living.

When the Vatican observatory priest sees the appearance of a comet, the Church is sure that it confirms the eve of the Armageddon. Meanwhile, the USA President's godson Robert Thorn is informed in the maternity in Rome by Father Spiletto that his wife Katherine has just lost her baby and she had troubles with her uterus and would not have another pregnancy. Spiletto suggests Robert that another just born child that lost his mother could be the substituted for his son, and Robert accepts the child and gives the name of Damien. Robert is promoted to ambassador in London after a tragic accident. When Damien's nanny commits suicide in his birthday party, a substitute, Mrs. Baylock, comes to work and live with the family. Along the years, Katherine realizes that Damien is evil, while Robert is contacted by Father Brennan, who tells him that Damien is the son of devil. When the priest dies in a bizarre accident...