Season 2 Episode 10 - Red Museum 

While investigating the connection between the abduction of several teenagers and a rural religious cult, Mulder & Scully discover a secret test being performed on the children using the "Purity Control" alien DNA from 'The Erlenmeyer Flask'.
parole chiavi: x-files, mulder, scully, full episode, season 2, episode 10, 2x10, red museum