The Cigarette Smoking Man persuades Scully to join him on a trip to retrieve extraterrestrial technology that can be used to cure all human diseases.
Tropes used in this episode:
Anger Born of Worry: A much less overt example of the trope than is typically seen. Mulder becomes increasingly worried and tense the longer Scully is with CSM alone, and becomes moreso when Scully refuses communication with him. When she returns, Mulder radiates anger, though this is seen through his body language rather than anything he says—silent and averting eye contact. The latter is the most noticeable for two people who are well-known for their Facial Dialogue.
Double-Meaning Title: As mentioned below, the title means "as friends" but sounds like "enemy" playing into the duplicitous theme of the episode.