A young American diplomat and his wife experience the joy of becoming parents in Rome, where their child is born. However, their happiness turns to deep sorrow when they are informed that their newborn has died. The hospital chaplain suggests that the couple adopt an orphaned infant whose mother died in childbirth on the same night. Desperate to spare his wife the agony of their loss, the diplomat agrees, and they raise the boy as their own, never revealing the truth about his origins. As the child grows, peculiar and alarming events begin to unfold around the family, suggesting that there might be a sinister force at work in their lives.

The diplomat is promoted, and the family moves to London, where the child's behavior grows increasingly disturbing, coinciding with a series of gruesome deaths and bizarre occurrences. A mysterious priest approaches the diplomat with a dire warning, claiming that the child is not what he seems and that he harbors a dark and terrifying destiny. Skeptical but troubled by the priest's assertions and the escalating danger surrounding them, the diplomat begins to investigate. His search leads him into a chilling conspiracy that spans centuries and suggests that his son may be connected to an ancient prophecy heralding the arrival of a malevolent force. As he delves deeper, he is forced to confront the possibility that saving his family may require an unthinkable sacrifice.