In this case, our heroes respond to a distress call and arrive to find a mass suicide. We briefly see the incoherent ranting of the final log entry. "Must destroy ourselves! Alien upon us. The enemy from within. The enemy!" Later, Spock plays the disturbing portions of the log, and they are a fine example of the descent into madness. I should mention here two nits some people pick with the log. One is that the final star date is actually after Kirk and the Enterprise crew arrive to find everybody dead! Well, okay, everyone knows star date is a godawful mess to begin with. This little glitch could be solved by editing a few words and does not go to the core of the premise, so I do not consider it a big deal. The other is that the log, which he presumably recorded into his tricorder somehow shows Starnes from in front, holding his tricorder. That it strange but, again, it could have been fixed simply by showing a closeup shot. It does not affect the basic premise.
In the first disturbing entry, Starnes, though calm and in control, remarks that he is having some strange feelings of anxiety, and all the other colonists have them too, except the children. The next entry shows him with an acute case of the jitters, saying the anxiety is getting worse. The next one starts out calmer, as he says that Professor Wilkins finished his excavation today and found that an earlier civilization was destroyed in a natural catastrophe, but one of them took refuge in the cave. This is significant because earlier on Spock got some strange readings from the cave and when Kirk when in he got an anxiety attack so bad that he most uncharacteristically panicked and ran out. The log continues to say that all of them are becoming more apprehensive, as if some unseen force were influencing them. At this point Tommy disrupts the transmission, so Kirk and Spock withdraw to watch the rest of the log in Kirk's quarters, with McCoy.
I am not quite clear whether what we see in Kirk's quarters is intended as a different log entry or a continuation of the last one. Certainly his jitters are much worse than when the log was disrupted. The last time he was calm at first, and only beginning to get nervous at the end. Now he goes from acute jitters to complete meltdown. This is the final entry that we saw the tail end of at the beginning;
I'm being influenced to do things that do not make sense. I even went so far as to call Starfleet Command to request a spaceship to be used as a transport. It was only when I couldn't tell them what I wanted to transport that I began to realize that my mind was being directed. I decided to send a dispatch to Starfleet, warning them. God forgive us. Must destroy ourselves! Alien upon us. The enemy from within. The enemy!Spock says that he never completed the entry and the dispatch was never sent, that whatever overwhelmed him must have done so at incredible speed or he would have provided details of the experience. Um, isn't that what he was doing in the earlier logs? But I will agree that his degeneration at the end does, indeed, start accelerating and gains momentum very quickly. But I would like to know whether his complete breakdown happened almost at once after the expedition disturbed something in the cave, or whether there was a delay. Nor is it entirely clear whether the distress call mentioned at the beginning is the same as the transport ship he requested and realized was a mistake. I supposed it doesn't really matter; either way the evil power is looking for a ship to get off the planet.
Other than that detail (well, and the two little nits that are easily corrected), I like the log. It works quite well. So well, in fact, that I would leave the log almost unchanged and modify the episode to fit it. For one thing (as I will discuss more in the next post), we should hear a lot more about that cave and what they found. It appears to contain the secret of the planet. Yet the whole cave angle goes nowhere and apparently seemed so pointless that it was actually cut in syndication. The other is that the symptoms on the log work a lot better than the ones on the Enterprise. The log describes a classic descent into madness. First they are uneasy. Then it gets worse. They try to distract themselves with work, but the sense of apprehension continues to grow. They start doing strange things without understanding why and begin to suspect that they are being controlled by an external force. And then complete breakdown and mass suicide.
That is not what happens on the Enterprise. Instead, they simply change course to Marcus XII without being aware of it, and without any strange psychological symptoms.* Some notice they are off course and others do not. But they all behave more or less normally until they realize the ship is off course and the Gorgan appears right in front of them. Then the children awake their "beast" and the all break down entirely, though without any suicidal tendencies. What should happen is that after the children beam up, the crew should start feeling strangely tense and anxious. At first they may just attribute it to seeing some disturbing sights. But the anxiety keeps getting worse. Maybe people even start doing strange things for no discernible reason. And then they view the log and see that this is exactly what happened to the colonists on Triacus right before they went mad and committed mass suicide. . . . .
*Well, except the big fight the guys in engineering put up when Scotty tried to take over and return them to the planet.