A Matter of Time, TNG 5
Matt Frewer (Max Headroom to you) shows up all Q-like as a historian from the future, just here to “observe.” It drives everyone bananas, esp. as Picard has to make a key decision regarding the aid of a needy planet. Indeed, Picard wrestles with his soul w/r/t the Prime Directive in an epic monologue that is, all kidding aside, quite compelling. Then there’s a third act twist I don’t want to give away that really pulled the rug out from under me when I saw this back in 1991.