Sherry Burton, Jillian McWhirter, a professional woman, discovers she is pregnant, and this news brings joy to her husband Craig Burton, Arnold Vosloo an emergency room surgeon. Yet the couple is haunted by unsettling memories from the night of conception, when Sherry is abducted by pale, grey extraterrestrials. As the pregnancy unfolds, Sherry begins to experience chronic pain and other unusual side effects, while Craig starts having episodes of missing time. The fear that she might be carrying something alien inside her grows from uneasy suspicion to outright terror.
To seek answers, they turn to their therapist, Dr. Susan Lamarche, Lindsay Crouse, but she offers no satisfactory explanation. Craig then asks his colleague, gynecologist Dr. David Wetherly, Wilford Brimley, to examine Sherry and perform an ultrasound. The ultrasound reveals that the baby bears an abnormal, almost inhuman appearance, and Wetherly suffers a massive heart attack soon after, later dying of cardiac arrest before he can confirm his findings. Craig becomes convinced that aliens are involved, and the sense of menace deepens.
Sherry’s behavior grows increasingly erratic, and she is hospitalized for pneumonia after spending hours submerged in an ice bath. In his search for answers, Craig turns to UFOlogist Dr. Bert Clavell, Brad Dourif, who explains a chilling history: aliens have been abducting humans to experiment on them, and their method of artificial insemination of Sherry is one of their recurring tactics, likening it to the way animals are tested in laboratories. Together, Craig and Clavell enter Sherry’s hospital room and Craig uses sodium pentathol to hypnotize her in an attempt to recall the abduction. They succeed, but Dr. Lamarche interrupts and has them removed.
Undeterred, Craig returns to the hospital with Clavell to take matters into his own hands. He plans to surgically remove the alien fetus and, more radically, to temporarily flatline Sherry so the aliens will believe she is dead and remove the fetus, granting him a four-minute window to revive her. Clavell, horrified, declines to aid and leaves. The surgery proceeds, but when Craig attempts to revive his wife, he discovers that he is thirty minutes too late—the aliens have used their power to induce missing time to thwart him. Craig is arrested for Sherry’s murder.
An unspecified period later, Craig remains imprisoned for Sherry’s murder, while the aliens return once more and abduct him from his cell, leaving his fate and Sherry’s future shrouded in mystery as they vanish to parts unknown. The story unfolds with a steady, restrained pace that emphasizes the psychic strain on the couple, the fragility of trust, and the chilling possibility that humanity may be only a small part of a much larger, indifferent cosmos.
