Robert and Katherine Thorn seem to have it all. They are happily married and he is the US Ambassador to Great Britain, but they want more than to have children. When Katharine has a stillborn child, Robert is approached by a priest at the hospital who suggests that they take a healthy newborn whose mother has just died in childbirth. Without telling his wife he agrees. After relocating to London, strange events - and the ominous warnings of a priest - lead him to believe that the child he took from that Italian hospital is evil incarnate.

Now come into his full knowledge and power, the Anti-Christ in the body of Damien Thorne is about to strike his final blow. The Christ-child has been born again, on the Angel Isle, Great Britain (Scotland, England & Wales). The plan is simple, find the male children born on the specified day, and kill them all.