I have some issues with it, but I find "Scotty is possessed by Jack The Ripper!" a premise so delightfully insane that it justifies the episode all on it's own. "Wolf In The Fold" is saved.
THE CHANGELING
THE APPLE
FRIDAY'S CHILD
THE DEADLY YEARS
RETURN TO TOMORROW
ASSIGNMENT:EARTH
^^this
It's a real mixed bag, but a watchable one nonetheless. The story goes out of its way in setting up Scotty as being a rabid murderous misogynist solely because an accident in Engineering from a female technician caused him to bump his head against a bulkhead - just so now Dr McCoy can shovel it on thick to the audience that he's going to hate all women and thus be a legitimate suspect for 45 minutes, apparently... (thankfully we get a scene where he's later caught red-handed, pardon the single entendre, which shakes things up a bit.)
...to the point that our Aberdeen Agent 86 there is going to go all stabbywack on every woman when convenient. Never mind this same setup is repeatedly sledgehammered as the episode traipses by, in case people were hoping the worst of it was brought up before the opening titles music started.
And yet the premise is so over the top that it almost becomes fun to watch just to see what the writer does with this bonkers premise and the payoff is pretty much worth the wait as it turns out to be *drumroll* Jack the Ripper, not related to the Jack who went up the hill with Jill to fetch that infamous pail of water. Also, there are enough clues dotted about - the missing knife, Hengist walking in as the psychotricorder technician beams in (and the technician being female, who would guess incorrectly that she wouldn't be the next victim to be stabbed by Scotty and his blade), Hengist revealing early on he's not from
Risa Wrigley's chewing gum pleasure planet Argelius II, and so on, that stay just under the radar by the moment any fan of the episode watches it a second time all those clues just stand up and wave prominently, which is actually surprisingly fun.
Nor will I ask how Redjec can go from one organic squishy brain to another but then plop itself into a bank of hard silicon chips (only to go nuts when Spock tells the computer to calculate to the last digit the numeral Pi though we were all hoping it'd be Kirk, except Kirk always kills a computer with illogic and we need the Enterprise intact, so we sic Spock onto it instead as Spock - per one of many of McCoy's quips - is more inclined to
marry it instead, "the right computer finally came along"...), but that whole scene where McCoy is drugging them all up is a genuine riot.
That, and character actor John Fielder pretty much steals the show in this episode. He's great fun to watch in "Get Smart" and other shows of that decade, and several others too.
The episode has moments worthy of much dislike, in due partly to being so wrenchingly contrived (it'd make a little more sense of the technician was being malicious against him but that's still a truly nutty degree for anyone to take - to murder anyone... never mind the level of stereotyped sexism involved as to why Redjac only kills women), but in season 2 it's nowhere near the worst of the lot. Rolling along with this story and there's still fun within the morass that quite defies description.