Kirk and crew land on a lonely planet where the sun is about to explode. They intend to evacuate the inhabitants but find the place deserted except for a Mr. Atoz who operates some sort of high-tech library. Despite trying to get a straight answer from him about everyone's whereabouts, Atoz is indifferent to their questions and insist they must quickly 'make a selection while there is still time'. They have no idea what he's talking about but wander about looking at the hand mirror-like disks on the viewers and they see images of the planet's past. Then, while a disk is in the viewer, Kirk runs through the doorway and is magically transported back in time to what on Earth would look like the time of Louis XIV (the 1660s). When McCoy and Spock follow, a different disk is in the viewer and they are sent to an ice age hell. All too late they realize that the library is a time travel machine and repository.
While Kirk's visit is pretty short and not all that exciting, Spock and McCoy's is much more eventful, as Spock falls head over heels for Mariette Hartley--who was sent to this awful place as a punishment. The scenes with Spock are exceptionally interesting and very atypical of the normally logical guy.
Spock's departure from the norm, the wildly inventive script and very diverse locales make this an exceptional episode--one well worth seeing.
FYI--Ian Wolfe, the excellent character actor, played Mr. Atoz. I am a huge fan of older films and have seen him as a supporting and bit player in countless films in the 30s and 40s and he looked almost exactly like he did in this episode from 1969. Interestingly enough, despite looking ancient, he lived on another 23 years--dying at over 95 years of age!!

This sounded like a really interesting movie from the blurb. Nazis, occult , government conspiracies. I was expecting a low budget Nazi version of the DaVinci code or the Boys from Brazil or even Shockwaves. Instead you get something quite different, more psychological, more something like from David Lynch. That was actually a plus. But the way the story is told is just awful.
Part of the trouble is the casting. Andrienne Barbeau's character starts off the moving being somewhat timid and afraid. She just doesn't do that well, even at her age, though she certainly tried. The actor cast as the son apparently thought this was a comedy. Most of the other actors also seemed to have thought this was a campy movie, or at least acted like it, rather than simply being quirky. The only one that I thought did really well was the daughter, Siri Baruc.
Another big part is the pacing. It starts off very slowly. So slowly you might be tempted to turn it off. But then it gets compelling for a while when you get to the daughter's suicide and the aftermath. But shortly afterward, it all becomes a jumbled mess. Some of this was on purpose, but much of it was just needlessly confusing, monotonous, and poorly focused.
The real problem, is it's simply not a pleasant movie to watch. It's slow, dull, none of the characters are likable. Overuse of imagery and sets. Some movies you see characters get tortured. In this, it's the viewer that does. It does have a few creepy moments, most notably the creepy Nazi paintings and the credits, but the rest of the movie is mostly just tiresome.