The Changling is the story that was the basis for the first Star Trek film. It's the 32nd episode broadcast and it first aired on September 29 1967. The Enterprise is heading for a planet which sent a distress call. They arrive to find the planet gone. A small metal probe attacks them with a powerful energy blast. They contact it and it stops attacking. They beam it on board the ship.
It's an old Earth probe called Nomad that was created by someone called Roykirk. It thinks Captain Kirk is it's Creator. That's why it quit attacking. It looks around the ship and wonders why all the humans are infesting the ship. Spock merges with Nomad and finds out it had merged with another probe from some other race. Nomad now thinks it's job is to search for imperfection and destroy it. People are imperfect so they have to go. Kirk talks the probe into blowing itself up because it is imperfect. The whole episode takes place was on the Enterprise. Not many shows don't have a planet visit.
Mirror, Mirror was first shown October 6 1967 and it was written by Jerome Bixby. Kirk, Bones, Uhuru and Scotty are visiting on the planet Halkan. It's a place rich with Dlithium Crystals. Kirk is there to negotiate a treaty for mining rights. Beaming back to the Enterprise the landing party winds up in a parallel universe where the Enterprise is part of an evil Terran Empire. You can tell it's evil because of the clothes and facial hair.
The Captain and the landing party get by as best as they can. The alternate Enterprise is a dangerous place. The crew advances through treatchery and murder in that universe. Kirk tries to get out of having to blow up the Halkan's and Evil Spock figures what has happened. He aids them into getting back to their own universe. Mostly he wants his Captain back. Another pretty good episode.
A week later The Apple appeared. The Enterprise landing party beams down to Gamma Trianguli VI. It's a nice looking planet but deep down there are some problems. Several crew members are killed and Mr Scott tells the landing party they are stuck. The tranporters aren't working and he can't beam them back on the ship. Something on the planet is draining the ships power.
They encounter some natives who live a simple live under the control of the big snake head. That's where the force draining the ship is coming from. The Enterprise blasts it and frees the natives. Now they get to live on their own. They learn kissing from the crew so they should be ok.
The Doomsday Machine was written by Norman Spinrad. I had read some of his earlier books but not anything much after the mid 1980's. It was the 35th episode in production, and broadcast, and it debuted on October 20 1967. William Windom starred as the Captain of the Constellation. He'd come up against the planet eater and lost. He tried to save his crew but the giant thing ate them.
Kirk and Spock speculate it might be some sort of Doomsday machine that's gotten out of control. They aren't having much success destroying it. William Windom takes his failing starship and plunges into the maw of the beast to put a stop to it's rampage across the galaxy. When the Constellation explodes it leaves a huge dead shell floating in space. William Windom revises his character in the Star Trek Phase Two series. I haven't seen those yet so I don't know how that works. I'll get to them once I'm done with the third season. All in all not a bad group of episodes with a nice variety of stories. There aren't any extras on the disc what with 4 episodes.