Jessica Barrett, a young English mother living in
San Francisco, reveals to her
music executive husband, Robert, that she is pregnant. The couple already have two young children: a son, Ken, and daughter, Gail. Several days later, during Ken's birthday party, Robert finds Jessica violently ill and vomiting in the bathroom. After visiting Dr. George Staton, her
obstetrician and personal friend, Jessica is informed that she is in fact three months pregnant, not the mere weeks she believed. Over the course of her pregnancy, Jessica finds herself subject to violent mood swings, apparent hallucinations of voices, and
poltergeist phenomena. On one occasion, Jessica is awoken by disembodied wheezing, and
levitates into the air and wheezes violently all through her house. George confides in a worried Robert that Jessica's pregnancy is progressing at an unbelievably rapid rate. Fearing for her wellbeing, George arranges for Jessica to spend time with his wife, Barbara, hoping she will confide in her. Jessica tells George she wants an
abortion, but swiftly vacillates, accusing him of being a murderer when he agrees to an abortion should he find the pregnancy a hazard to her health. The Barrett household soon becomes a hotbed of supernatural activity that terrorizes both Gail and Ken when their father is away. Meanwhile, Jessica exhibits increasingly horrifying behavior akin to
demonic possession, such as inhumanly twisting her head, wheezing and projectile vomiting. Robert is contacted by a mysterious man named Dimitri who instructs him to sequester Jessica in their house and keep visitors away, assuring that the child is born. Jessica grows progressively ill, exhibiting a fever, stomach ailments, and other bizarre symptoms, and becomes bedridden. Under Dimitri's instructions, George has Jessica placed in a
straitjacket to prevent her from violently lashing out. When George visits her, Jessica alternately pleads for his help before cursing at him in a deep, demonic voice. George has Jessica undergo a series of tests, including scans of her brain, but none of them show any neurological anomalies. After Robert is subject to a torrent of violent supernatural behavior from Jessica, it is revealed that Dimitri is a lover from Jessica's past, and that he is a
Satanist who has arranged for her to give birth to the
Antichrist, in exchange for the demonic spirit having saved him from dying in a car accident years prior. In a violent confrontation between Jessica and Dimitri, the demonic entity turns on him, and implies that all of the events that have taken place were arranged for its own amusement. The entity murders Dimitri before departing Jessica's body, after which she immediately has a
stillbirth. Some time later, a healthy Jessica accompanies Robert and their children on a boat ride in the
San Francisco Bay. Ken unwraps a gift he earlier acquired on his birthday, concealed in black wrapping paper with a gold ribbon. The gift is revealed to be a red toy car, the same model Dimitri crashed in the accident that nearly claimed his life. Ken drops the toy car over the edge of the boat railing, and his eyes glow green, implying he is the actual Antichrist. ==Cast==