It sounds like an exciting episode, right? No, not really.
Shatner's reaction to having read this episode's script.
Conveniently, the Enterprise is at the center of the winking out effect. They head down to the surface of the planet below where they unfortunately encounter the show's central character - Lazarus.
The good and evil Lazarus switch places over and over and over, seemingly endlessly so with an effect that brings in a shot of the Trifid Nebula and a sort of a negative shot of the two of them fighting in slow motion.
They bring Lazarus aboard the ship and, even though he is at the center of the winking out effect and that both Kirk and Starfleet think that this might signal an invasion, they let him wander about the ship unattended.
Then we find that there is a source of radiation on the planet below.
As we eventually learn there are parallel, but opposite, universes that are threatening to annihilate each other. Cool, eh? Lazarus is the key to keeping the universes safe from annihilation.
The solution is for the Enterprise to destroy Lazarus's space ship (which is also a time machine, but nothing is really made of that) while the two of them are in the magnetic corridor thing, fighting for all eternity. The sane Lazarus is cool with that. As he says "Is it such a large price to pay for the safety of two universes?"
This was my 20th of these. I hope that some people are enjoying them. Next up: Tomorrow is Yesterday.