At the start of the show, Kirk, Spock and Bones beam down to a library.
The solar system of the library's planet is about to go supernova any minute and the world was seemingly devoid of all signs of life, so even though it's an incredibly dangerous and utterly pointless mission, the Enterprise crew has decided to stop and poke around this one particular building on the whole wide planet in the ticking-down seconds to Armageddon. I figure Captain Pervert made the ship stop because he couldn't bear the thought of so many naked lady fine art books getting blown to cosmic dust, so he wants to grab up as much high class porn and high tail it back to the ship before all traces of tasteful nudity in the entire solar system are wiped out forever.
Kirk is running out the door with an armload of Interstellar Hustlers and yelling for Spock to grab as much as he can carry from the special DVD room behind the hanging beads when an old man jumps out from behind the card catalog and demands to see his library card.
When I was a kid, a friend of mine who didn't feel like going through the three-second hassle of checking something out of the library tossed books out the second story window and collected them on the ground outside. True story.
The same old man is hiding around every corner Kirk runs around. It turns out the old librarian is triplets, but some of him are robots or holograms or something and only one of him is really him. Insatiably curious science officer Spock never bothers to ask what the other versions of the librarian are made from, and chief medical genius McCoy never bothers to find out. It's a good thing the Enterprise sent the A team down to scope things out instead of Chekov and Uhura, who would have just wasted time looking up books on male pattern baldness and fan dancing around the magazine racks until the joint blew up. An inquisitive eight year old would have at least poked the duplicates with a stick.
Kirk and pals find out that the real old man is bachelor number three. His name is Atehorse, so I assume he's a Burger King customer. Have it your way, provided your way is a saddle in two buns and not the other way around.
Mr. Atehorse tells them that they're late and that everyone else on the planet is gone. Apparently this building is the Ellis Island of the whole planet, and everyone on the entire world has filed through one small door out back. Let's see, there are seven billion inhabitants on Earth. So if all seven billion had to go to only one library where we all had to sit down one at a time to figure out where we're going, and then we all had to schlepp through just one small door to get there, to process everyone through would only take about...wait, let me get out my abacus. Fifty-million billion trillion years. Good thing in Star Trek there's never more than eight cowboys or gangsters on a whole planet or they'd be stacking Porta-Potties a thousand deep for those lines wrapping around the equator.
The old man loads a giant watch battery into a DVD player, and Kirk watches The Three Musketeers.
Suddenly an invisible woman screams through a strange portal in an eerie library run by a creepy old man on an uninhabited planet that's about to blow up, so naturally Captain Genius leaps through into the unknown without even asking if it's maybe the Dolby Surround Sound on the movie he's watching turned up too loud.
When Kirk was bravely leaping through a mysterious portal and falling twenty stories into a wood chipper, Bones was watching the snow forecast on the Weather Channel on a TV out back. He and Spock, unlike Kirk, at least have had the benefit of seeing somebody else who just jumped through the door evaporate into thin air. Instead of turning to the librarian and asking, "What the hell?" the Stupid Twins leap right on through after Kirk. Maybe the Federation is like the Golgafrincham B Ark, and Starfleet is just a clever ruse to get all the morons off Earth.
Kirk ends up back in time in Revolutionary France, but not the Earth one. This is the Revolutionary France on an alien planet that apparently also, incredibly, had its own Revolutionary France, right down to the pantaloons and feathered hats. In an incredible stroke of luck, however, everyone on Alien Planet Revolutionary France speaks English and not French or especially Alien French, so that's nice for Kirk, who won't have to point to the menu and yell increasingly louder at snooty Alien Planet French waiters that he wants the BLT sans snails.
Kirk defends a hideous slattern in a sword fight with a musketeer. So a guy from the future beats a guy from the past with the guy from the past's own weapon. See? And here you thought teaching Starfleet recruits to be experts with a weapon that fell out of use half a millennia ago was stupid. This is exactly why West Point will never drop its controversial "Defending Your Cave with Big Rocks and Sharp Sticks" requirement.
Spock and Bones land on ice planet Hoth, which is ten feet of white Styrofoam walls and a couple of guys in the rafters shaking out feather pillows.
Back in Three Musketeer land, Kirk says he's going back to the library but finds that the door has been replaced by a Paramount back lot wall, some pickle barrels and a giant boat chain. He yells at the wall and Spock and McCoy holler back from the Safeway freezer aisle. The filthy slattern accuses Kirk of being a witch who talks to ghosts, and since he weighs the same as a duck, D'Artagnan tosses him in yon slammer and verily throws away ye merry key. Good God, the writing is terrible.
Meanwhile, back in the ice age, Spock and Bones know they walked through some kind of portal, they could hear Kirk yelling back at them through it, so rather than look for it they naturally leave the spot where they heard Kirk talking and stumble away into a blinding snowstorm. You know, it's like how they always tell you how if you get lost in the wilderness you should always run away from the barking St. Bernard to play in the avalanche.
Bones wanders around the snowscape flapping his hands and announcing he's got frostbite. I'm not a fancy space doctor, but I'd think it'd be a good idea to try to keep them warm. Stick your hands into the opposite sleeves like a makeshift muff, pull them up inside their own sleeves, pull them right up into the torso part of your shirt and stuff them down your drawers. Instead, Chief Medical Officer Dummy rolls out snowmen barehanded in eighty below weather for an hour and then complains that his fingers are kinda sorta numb. When someone comes to sickbay with a headache he gives them two aspirin and a hammer to bang them in.
By the way, if you toss an alligator on a North Pole ice floe, it probably wouldn't last too long. So how is it that Spock, who comes from a million degree fire planet, is somehow tougher than Bones in the cold and isn't the first one turning blue and dropping over like a Spock-sicle? Wait, forget logic...what is this mysterious figure rising up out of the pillow feathers? Please let it be an NBC executive holding the Star Trek cancellation memo.
Nope, it's just the Eskimo Grim Reaper.
The Grim Reaper in a white Nanook parka brings Spock and McCoy back to its cave lair. It takes off its hood to reveal a horror greater than the ghastly specter of Death personified. It's that deeply annoying Mariette Hartley woman my TV kept trying to foist on me in rotten failed sitcoms, irritating guest appearances and those stupid Kodak commercials costarring Jim Rockford throughout the 1970s. Death ain't looking so bad right about now.
Over in the Musketeers picture in Theater B, Kirk gets locked in the slammer and some judge who's a dead ringer for Charles Laughton turns out to be from the future too. Kirk yells "library" and Charles Laughton reacts like the Knights of Ni when someone says "it" and runs off to make Clark Gable walk the plank.
Spock finds out that phasers don't work again, which puts the malfunction rate up near 98%. I'd back a Pinto through a dynamite factory before I'd rely on one of those things to save my hide.
That irritating Hartley woman says her name is Clarabell, but she dropped her seltzer bottle and whoopee cushion out on the glacier. A clown costume would actually make more sense on an ice planet than the leather bathing suit she's suddenly prancing around her cave in.
The old man in the library sent everybody on the planet back in time because Krypton was blowing up, and Clarabell says the Activision process alters cell structure and brain patterns so that people once sent to the past can never go back to the future. Because, see, not only the basic cell structure of a human being was different a hundred years ago, so too were his very thoughts. This kind of makes sense, because in 2013 this sounds like the stupidest pile of steaming bad writing and crap pseudo-science baloney I have ever heard, but in 1969 it was apparently an example of cutting-edge space-age smartness.
Back in his cell in Ye Olde Crappe Storie Towe, Kirk gets threatened by one short fat guy with a blunt-tipped sword and mocked by the ghastly slattern who he saved but who now yells at him that he's going to get burned for being a witch. I'd screw chivalry and punch her in her pox-riddled kisser, then pray that my moron chief medical officer could figure out what bottle of colored water back in sickbay is the cure for fist herpes.
Okay, just this once if you'll help me escape. But it doesn't make me gay.
Charles Laughton helps Kirk escape and he walks through the wall back to the library where the old man knocks him out with a flashlight beam and tries to roll him back through the door on a Radio Flyer wagon.
Meanwhile, back in Siberia, genius Spock says he's going to build a greenhouse, which is nice but is about as practical as building a smelting plant since there are no seeds, dummy.
Time travel has made Spock start regressing to a warlike primitive like his Vulcan ancestors of 5000 years before. Whoops! I hope I never go back in time; I might start building pyramids!
Spock has a burger, makes out with the broad, smacks McCoy around a little. This is all supposed to horrify us but, you know, I'm really not seeing what we're supposed to think is all that wrong about Caveman Spock.
Okay, yeah, he then tells Mariette Hartley that she's beautiful, but obviously that's a lie because he has eyes. He probably just wants to get her out of the way of the TV so he can watch the game in peace for once.
She says she has "longed" to hear him say how beautiful she is. Sister, he hasn't even been there for three hours. You caveman chicks put too much pressure on a guy. McCoy agrees, and before she starts asking him to help her hang curtains and rearrange the rocks he runs out of the cave wearing a tiny furry dishrag to ward off the deadly cold that almost killed him ten minutes ago.
Back in the future, Kirk beats the crap out a hundred year old librarian. Surprise!
Spock and Clarabell follow McCoy and his furry dishrag back to the Styrofoam ice wall where Kirk hollers out to them. Spock tries to push Bones through alone, but they figure out that the two of them have to go together. They go back, leaving Clarabell to cry tears that don't freeze in a blizzard of goose down.
Somehow traveling forward in time makes McCoy's furry dishrag vanish by the time he hits the library, and Spock immediately reverts back to his old self. I guess because his cell structure and brainwave patterns have reverse-polarized the DNA matrix of the temporal flux time eddies chrono-particles. Probably.
Scotty yells down from the ship that they only have seconds to beam up before the sun blows up, and I realize that I never once saw Scotty this episode, and I wonder how little the cheap Paramount bean counters paid the actor to shout a couple of lines into a tape recorder. C'mon, give the guy a break. Scotty won't have another acting job until the first Star Trek movie in 1979.
Kirk and the others leave the planet in the nick of time, having learned absolutely nothing about the people, their culture, the animal life that must still exist on the world unless it too was sent through the portal, how the entire history of the world wasn't altered by sending everyone from the current age back in time, why the people who built the time machine didn't send people back just fifty years to warn people of the coming apocalypse so they could build spaceships and take off...you know, all that explorer stuff they're supposed to find so interesting.
Job well done, fellas. I guess with only one Star Trek episode left the only question left in the universe is why chicks can't fly spaceships.