The GREAT episode, of course, is Norman Spinrad's superb "The Doomsday Machine." Essentially a ship-bound story designed to cut budget corners, this is one of classic Trek's finest hours. Featuring the cast in high form and the addition of guest star William Winham as the obsessed Commodore Matt Decker, the tension is palatable. All the elements of great sci-fi and classic Trek are on display and the conflict between Decker and Spock is not to be missed. Yes, the effects do look a bit dated, but when you've got a superb story and well realized, three-dimensional characters, you can overlook such flaws.
As for the good episode, Wolf in the Fold is it. Dealing with Scotty and giving our favorite engineer a bit more to do that talk about his engines, this episode lacks the punch is should have. And coupling with the Doomsday Machine will bring it down by comparison. But it's still an enjoyable enough adventure that is worth viewing by any Trek fan.
Well, at least Keough does seem to like Wolf in the Fold. This is a far-fetched, but entertaining whodunit. Like Keough, I liked the performance by John Feidler. Like William Windom, he is a veteran character actor who always manages to add a great deal to any film/TV episode in which he appears.
In fact, my own (minor) complaint is with the cover. Nichelle Nichols is pictured on the front, but does not appear in either episode on the DVD!