 B.J. awakens from a nightmare covered in blood , finding the word " Sister " slashed into her chest . She also sees a young Cokely reflected in the mirror behind her . She heads to a stranger 's basement and tears away the floorboards , revealing the skeletal remains within that is found to be of the missing Ledbetter 's . Cokely is arrested , but denies attacking B.J. , insisting he 's too old to even leave his residence without his large oxygen flask . Scully tells Mulder that blood on the latest victim matches Cokely 's . The agents visit Thibedeaux , who describes her encounter with Cokely in the 1940s . Mulder notices a photo of her at the 1939 World 's Fair featuring the Trylon and Perisphere . When pressed , she reveals that the rape resulted in a child , which she put up for adoption . The FBI tracks down the child , who turns out to have been B.J. ' s father , causing Mulder to surmise that B.J. is the killer and may be operating on genetic memories which tend to skip a generation . 
