Scully and Mulder are called into investigate a strange case of a man found sitting in his backyard having been exsanguinated and having two bite marks on his neck. The man's daughter, Teena, only remembers seeing what she calls red lighting. They've barely started the investigation when they learn there has been a virtually identical attack on the west coast. When they meet that man's daughter, Cindy, she is identical to Teena. Deep Throat provides Mulder with information about the Litchfield experiments, attempts at gene modification where children, named Adam and Eve, were produced. They trace a common link from the girls to Dr. Sally Kendrick who was fired for her position at a fertility clinic for experimenting in eugenics. The agents take the girls into protective custody but it's not the girls who need protecting.