"Wolf in the Fold," written by Robert Bloch, is one among the best episodes of Star Trek. A good mystery with an exciting premise. But what many probably don't realize is that the killer reveals himself BEFORE the big revelation later in the episode.
(SPOILERS) After Yeoman Tankris is killed while taking readings from Scotty, the group assembles in the main room, with Mr. Hengist (John Fiedler), arriving last, and two others. During the conversation, Captain Kirk says "There's been another murder, Hengist. One of my crew." Karas (Charles Macaulay) then says "The same as Kara (the first victim). A sentence or two later, Hengist asks "How was the girl killed?"
You'll notice at no point in the conversation did anyone mention the sex of the second victim. So how could Hengist know, unless....
Later, Hengist trips up again. No further details were provided to him concerning the second murder, yet he says "Need I remind you of the circumstances, Captain. In both cases, your friend Scott was discovered over the body. And later, claimed to remember nothing."
You'll notice that Mr. Spock is absent - still on board the Enterprise. I get the feeling this was not an accident, because if anyone could have quickly picked up on that, it would be Spock.
This is a true mystery in the classic sense, because Robert Bloch provides a few subtle clues allowing those who are paying attention to deduce the killer's identity early. But I'll confess it took me many viewings of episode before I noticed the clues.
