There are some episodes of Star Trek where Kirk rekindles a relationship with an old flame. There are other episodes where the crew meets a once-respected hero or mentor figure, only to realize that person has gone completely cuckoo for Cocoa Puffs. And there are still other episodes where they’re burdened with a civilian who snoops around and asks too many questions and throws their weight around and is totally overwhelming and annoying and in the way all the time.
The Entropy Effect contains all of those tropes, plus time travel.