The OSIR sets up surveillance of a top-secret meeting between the top brass of the military and genetic scientist Dr. Elaine Spurvey. Four years earlier, Dr. Spurvey had been with the OSIR but had left under a cloud of suspicion when the agency refused to endorse her proposal to create artificial humans. Their hunch that Spurvey has been biologically altering human test subjects is confirmed when the doctor unveils Lilith, the resulting prototype of "Project Regeneration".
Lindsay Donner goes to Spurvey's room and demands to meet Lilith. She is shocked to see the physical similarities between herself and the young prototype, and is further stunned by the revelation that Spurvey's access to the OSIR lab had allowed her to use Donner's DNA in her experiment. Outraged, Donner accuses the doctor of pushing the boundaries of science and morality, but Spurvey believes her discovery is the most important medical breakthrough since the discovery of DNA and plans to continue her work.
Meanwhile, Axon thinks he's seeing a ghost when his old colleague Connor Doyle shows up. Doyle was presumed dead, following an explosion during an OSIR investigation in Siberia three years ago. Doyle explains that the Russian military had been monitoring the operation and had managed to save him. For the next few years, they held him prisoner in a research facility in order to study an alien parasite that he had contracted during the fateful mission. He finally managed to escape, and when he heard rumors of Spurvey's Project, he knew it could only be accomplished with alien DNA. Since a sample of the parasite had been brought back from Siberia and was housed in the OSIR's lab, Doyle believes that Spurvey accessed the sample and used it to create Lilith's regenerative powers. The combination of this parasite with Donner's DNA, would make Lilith a hybrid í¹‚í¸¡lf human/half alien - whose violent alien traits become dominant in its third year of development. Though they know the situation must be contained, it's already too late. Lilith has already claimed her first victim - none other than her own creator, Dr. Spurvey.
While Donner is still trying to come to terms with Lilith's existence, she is faced with another shock - the reappearance of Doyle, the man with whom she had once shared strong feelings. Doyle suggests that, through a plasma transfusion, more of Donner's cells could be introduced to Lilith in an attempt to enhance her human side - and lessen her alien aggression. Donner agrees to the experiment knowing that, if it fails, Lilith's murderous alien cells will take over.
As they prepare for the transfusion, Lilith once again becomes violent as she expresses jealousy over Donner's obvious relationship with Doyle - one that had begun long before the accident in Siberia. They are able to contain her, and begin the procedure. It soon becomes apparent that Donner's blood is being sucked out of her at an alarming rate. An ultrasound on Lilith indicates that she is carrying a child - an alien life form - which is drawing on Donner's blood. As Donner screams in pain, Axon orders the transfusion be stopped immediately. Doyle stands by - a smile of satisfaction playing on his face.
What were Doyle's true motives for the experiment? Was the transfusion merely a sinister ruse to save the life of Lilith's alien child?