Years and years ago, I saw part of a Star Trek episode on tv. I remember almost nothing from the episode, except that near the end, an old man was lying on the ground. After speaking with someone who I think was the ship's captain, he ends (having been asked to explain his actions over the course of the episode, I think) with:
Because [pause] I was never really here.
Whereupon the man disappears, fading away.
Does anyone know which episode this might have been from?