In 1979, a newborn girl named Christine York is marked by Satanists, including her doctor, Dr. Abel, and her guardian, Mabel, as the one destined to bear Satan's son during the final hour of New Year's Eve, 1999. This revelation comes about as a priest at the Vatican observes a celestial comet, referred to as the "Eye of God," signaling the birth of this pivotal figure. Tasked by the Pope, the priest embarks on a mission to protect Christine from the impending evil. However, a faction of Vatican Knights, led by a corrupted cardinal, contends that she must be eliminated to thwart Satan's plans—a notion opposed by most of the clergy, including the Pope, who believe that taking a life to stop evil is inherently sinful.
Fast forward twenty years to the end of 1999, where retired cop Jericho Cane (Arnold Schwarzenegger) grapples with deep sorrow following the brutal murder of his wife and daughter at the hands of hit men. He now works for an elite security firm alongside his friend Bobby Chicago. During an assignment to protect a Wall Street banker, they find themselves ambushed by a priest named Thomas Aquinas. Upon capturing him, they unwittingly uncover that the banker is under Satan's possession and possesses formidable powers. As fate would have it, Satan brutally eliminates Aquinas, crucifying him on a hospital ceiling.
Determined to protect Christine, Jericho and Bobby begin their search for her after discovering vital clues inscribed on Aquinas's skin. After rescuing the now-adult Christine York from an assassination attempt by the Vatican Knights, tragedy strikes when Satan appears and blows up their getaway van, claiming Bobby's life in the explosion. As chaos ensues, Jericho confronts Mabel—a woman possessed by a supernatural force—who proves a formidable adversary despite her age.
With tensions rising, Jericho faces off against corrupt police officers, including Marge, his old superior, who are in league with Satan. After an intense confrontation, he faces demonic retribution when Satan resurrects Marge to further his own plans, sending the police on a search for Jericho and Christine. Seeking refuge, the duo turns to Father Kovak, who elucidates the dire situation: Satan aims to unite with Christine as part of a centuries-old prophecy.
> "Satan's greatest trick was to convince mankind that he does not exist."
Understanding the grave stakes, Jericho urges Christine to go into hiding. However, she chooses to remain with Kovak, leading to a confrontation with Jericho's inner turmoil as Satan attempts to manipulate him using visions of his lost family. When Jericho finally resolves to save Christine, his efforts draw him into a cat-and-mouse game with the Vatican Knights, who are also pursuing her.
As the tension escalates, Jericho's determination leads him to a climactic battle between good and evil, where personal sacrifices are made, and loyalties are tested. Betrayed by Bobby, and ambushed by Satan's forces, Jericho fights back against overwhelming odds. After a fierce battle within Satan's hideaway, he and Christine make a desperate escape into a subway car. In a final showdown, Jericho uses a grenade launcher to force an escape from the collapsing train, leaving Satan scrambling for a new host after destroying the banker's form.
No longer able to evade his destiny, Jericho finds himself in a church, praying for strength as Satan emerges in his true, monstrous form. In an intense battle for control, Jericho uses a statue of Saint Michael to free himself from Satan's grasp in a final act of redemption, enabling Christine's survival just as the clock strikes midnight. As the year 2000 dawns, Satan is cast back into the abyss, leaving Jericho to witness the serene vision of his family before he passes on, knowing his sacrifice saved Christine and prevented darkness from consuming the world. With New York rejoicing, Christine expresses her heartfelt gratitude to Jericho, forever changed by the extraordinary events of that fateful night.
