This is a beautiful story, for the most part it is told well, and it's ultimately haunting despite its problems. There are plot holes you could drive a truck through, but they are easy to forgive because of what happens to our characters. This is a complex script, marred in some respects by the creative team which saw it through to completion, but it shouldn't be faulted for that. It's still genuinely memorable -- and genuinely classic -- Trek.
There are three parallel stories, representing (for the most part) the best of Trek: the nova/library, Kirk's trip into the past, and Spock/McCoy's encounter with Zarabeth. Balancing these three stories, while giving each its due, is a tremendously difficult task which is handled here with great skill.
The library story, essentially just to set things in motion, is actually a great sci-fi concept in and of itself. Once you've invented a time machine, why not catalog all of the great events in history? And once you find out that your world is dying, it makes a perfect escape route. (Plot Hole #1: Why would a starship wait until a few hours before destruction to check out a planet about to be vaporized?)
The early scenes use a bit of ambiguity to draw us in, but the mystery doesn't last long. This is a sure sign of confidence in the material. It would have been easy to have the characters confused throughout the episode, solving the mystery only at the very end (as later Trek incarnations would make standard). Unfortunately, once they do figure it out, the creative team felt the need to hammer it home just in case even a single viewer missed it. Thus, after Kirk has given us the solution ("Apparently they've all escaped the destruction of their world...by retreating into its past."), they make Spock fill in all sorts of details that we really don't need ("Just before you disappeared, Captain, I discovered a machine..."). It would have made more sense for Spock and McCoy to begin immediately -- frantically and separately -- seeking out the portal. Then, unable to find it because they were not looking together, they are overwhelmed by the need for shelter. (Plot Hole #2: How can you converse with each other across time?)
Kirk's story provides something the networks always wanted: pure adventure. This story is beautifully descended from "Where No Man" and puts Kirk into a situation where he must be a swash-buckler, a gentleman, a con man, an escape artist. It has a historical period in which it's fun to see our 22nd century starship captain try to maneuver. He must use his wits and his physical abilities in order to escape. Some would have had Trek built around only stories like this. (Fortunately, Roddenberry had other ideas.) Best of all, this story ends at just the right moment, right before it loses its steam -- the timing couldn't be any better. (Plot Hole #3: Why doesn't the jailer fight? Why does the prosecutor return?) Kirk reenters the library and begins an intriguing close call story.
Meanwhile, the Spock/McCoy story is descended from "The Cage" -- the more cerebral side of Trek. These characters, trapped in a barbaric past, gradually becoming more barbaric themselves, get something much more serious and much more dangerous for their characters. These two have been at each other's throats for almost two full seasons. Forcing them to problem-solve together, when each is compromised, is the perfect way to explore this conflict a little deeper, perhaps to resolution. Having Spock shed his logic -- and McCoy exploit it -- is key. The story can then reveal that this relationship is much more complicated than some of the writers (Gene Coon) would have it. Spock refuses to leave McCoy for dead, but later nearly kills him. McCoy taunts Spock yet again about his lack of emotion, then helps him realize he needs what he has lost. The complex relationship is deepened and changed by what happens here.
Kelley and Nimoy play it beautifully. Each has some lines which are unnecessary explanations for the benefit of slow viewers. They downplay those as much as can be expected. Nimoy allows Spock to unravel gradually while constantly grasping for what has been his character's center. He genuinely seems to lose the character while trying to retain it, which is exactly what the story requires. Kelley resists the urge to fill McCoy with blind rage, retaining just enough reasoning-through-frostbite-haze to realize that they have a mutual problem. Then, when emotions do boil over, it comes from somewhere motivated. The part is well-written, and Kelley is up for the task (as always). His final scene, watching for Spock's reaction upon their return, is quite nuanced, a mixture of good bedside manner and the concern of deep friendship. He asks without words how Spock is doing, his face full of compassion and regret. With moments like this, the producers should have realized the great acting talent they had and relied on it more confidently to tell the stories.
The writing uses Zarabeth as a foil and not a center of the action, which is unlike most of the third season. This is not her story, and should not be. The character, beautifully (if simply) played by Hartley, merely exists to draw out Spock and McCoy and fuel what needs to happen between them. Her own backstory is actually a bit overplayed. We might have believed her character a bit more if we knew a little less about why she was banished (partly because her adversary had the unfortunately sci-fi name of Zorkon, which follows on the unfortunately clever name of the librarian). Spock gets the girl, which is quite plausible, and then immediately regrets it. But Hartley gets partial credit for that aspect working because she shows some subtlety in reeling Spock in with just the right inflection on the carefully chosen words. (Plot Hole #4: How does McCoy figure out that she's lying?)
Kirk may not be changed by his experience, but he will find his two friends very changed. That is one of the hallmarks of a great episode. (Plot Hole #5a,b: Why does the passage of time in the past run concurrent with passage of time in the present? Shouldn't Kirk, Spock, and McCoy emerge at exactly the same instant they disappeared?)
Some technical notes: The optical effect of the library portal is extremely well-done using slow motion to great effect. Zarabeth's costume is another magnificent creation (giving her fur boots under her fur coat is positively fiendish), though you can't help but wonder what it was about her bellybutton that offended censors so much when bellybuttons ruled the day a couple of weeks ago ("The Cloudminders"). The pirate costumes are a bit on the cheesy side, but forgivable given the nature of his story. Another guest star, Murdock, is splendid as the prosecutor who knows too much. Zarabeth's cave is a wonderful set, despite the fact that it looks like a set. Lighting is memorably good in both past eras. The multiple-Atoz device seems a bit forced (no doubt for cost-saving reasons) and added just so Kirk would have someone to karate chop later (but why, oh why, did he have to chop kindly old Ian Wolfe?).
But for the first and only time (that I can remember) an optical effect delivers the final emotional blow to the episode. As the Enterprise speeds away, the star goes supernova, and the planet -- with all its histories -- disintegrates, one can't help but wonder about all the pasts which are lost, and mourn Zarabeth with Spock.
Rating: Top (2)