This is more like it. In a season that is widely regarded as being the weakest of the original three, carrying a number of weak episodes, it is with welcome that this much stronger story comes along.
It is much sharper and more focused than many third season offerings, to the extent that it could easily have come from the far superior first or second seasons.
Mara is the first Klingon woman that we have seen in the franchise. As with male Klingons in the Original Series (in face, even more so), she is rather different from the Klingons of the big-screen movies, and incorporated into 'The Next Generation' onwards.
I like how the story unfolds, and a nice touch is that when we first see the alien entity moving around the ship, it appears almost casually, with no big music cue or anything to emphasise it.
This episode would be knocked out of my Top 10 favourites, but it certainly stands as one of the third season's strong stories. It's just a shame that more of the season wasn't of this quality.