 The only clue found at the scene is a Lucky Boy employee button . Mulder and Scully check all of the employees and discover that one of the clerks , Derwood Spinks , is missing his button . Scully suspects Spinks after it is discovered he has a criminal record . Mulder , however , believes that the victim 's brain was removed by a proboscis , and suspects another employee , Rob Roberts , of committing the murder . Rob , who is actually a mutant human who wears a disguise to hide his true physical body , subsists on brains in order to survive . When Sylvia is trailed by a private investigator ( Steve Kiziak ) , Rob kills him and eats in order to placate his hunger , which begins to get more and more uncontrollable . 
