TOS #29: Operation Annihilate

This is a relatively straighforward episode aboult slimy creatures, which are actually a hive mind, taking over the bodies of the people on Deneva and causing them to build ships to spread the creatures to other star systems. The things kill Kirk's brother and infect his nephew.



Spock also gets infected, but is able to control the pain used to manipulate his body and mind. He beams back down to capture one of the nodes of the organism.



The Captain figures out that the thing is sensitive to light, and they test the hypothesis on Spock. Light does remove the creature from him, but also (temporarily, luckily) blinds him. Before realizing Spock's blindness is reversible, this episode created a good-of-the-many/good-of-the-one scenario around Spock which is clearly one of the precursors to the plot of II.

TOS #28: The City on the Edge of Forever

Of all episodes of TOS, I believe this might be the one that affected me most, personally. In it, Bones OD and transports down to some weird anomalous ruins on an otherwise unremarkable planet. He jumps through this time gate into about 1930, altering the timeline significantly. The rest of the away party appears to be inside some kind of immuned area, as they are now trapped in an alternate timeline in which there is no Enterprise in orbit. The gate lights up when it talks, and it kind of insults Spock.

It agrees to replay Earth's history and Kirk and Spock try to jump back to just before where Bones went. They miss by what appears to be several weeks. Once they get back to 1930, Kirk meets Joan Collins and falls in love with her. Spock figures out that the timeline alteration is that Bones saves her. By saving her, he causes the US not to enter World War II in time, letting the Germans develop atomic weapons first and win the war.

Although Kirk is in love with her, he stops Bones from saving her at the critical moment and fixes the timeline. The gate thing then allows them to jump back to their own time and beam up to the Enterprise. The thing I like best about this episode is how Kirk and Spock work for pennies a day to buy parts which Spock uses to build a computer to interface with the tricorder to figure out what's happening to the timeline.

TOS #27: The Alternative Factor

While an investigating an uninhabited planet, the ship gets rocked by this strange force that makes things' gravity go momentarily near 0. The Captain, Spock, and several redshirts then beam down to talk to a newly discovered, single, humanoid life form on the planet, who they bring back to sick bay on the Enterprise.



This guy turns out to be schizophrenic, and one of his personalities is a dilithium crystal kleptomaniac. Eventually, they figure out that there is a singularity connecting parallel universes, and that this dude is actually jumping back and forth. The other him, from the parallel universe, is trying to stop him from accidentally annihilating everything.

Eventually, one of his selves and Kirk manage to lock both halves of the dude in this interstitial space, protecting both universes but dooming both incarnations of the guy to eternal hand-to-hand combat in a very blue room.