Science Fiction is at its best when it provides social commentary, and Star Trek is no exception. Many of the episodes address timeless issues. “Let That Be Your Last Battlefield.”, for instance, discusses racism. Interestingly, it was written after Martin Luther King was assassinated.
The Enterprise is on route to the planet Ariannus to decontaminate its atmosphere. Sensors detect a disabled stolen shuttlecraft. It’s brought aboard, and we meet its sole crewmember, Lokai, a political refugee from the planet Cheron. Lokai’s skin is white on one side and black on the other.
Moments later, another spacecraft is detected, but it disintegrates. However, another alien has now arrived on the ship. This is Bele, who is in pursuit of Lokai. Bele’s skin is also white on one side and black on the other, however, his color scheme is reversed. Because of this difference, he sees Lokai as beneath him. And not just Lokai, but everyone else.
Bele is very much like Inspector Javert, the antagonist from Les Miserables. He sees Lokai as a second-class citizen, similar to how blacks were seen by whites prior to the civil rights movement. The crew of the Enterprise has moved past such conflict, and to them Bele is a curiosity. They side more with Lokai than Bele. Bele wishes to return Lokai to Cheron, where he will receive judgment for his crimes. Lokai refuses because he feels his race should be seen as equals. Kirk wants to grant him asylum, but his hands are tied by Federation Law. So, he reluctantly gives in to Bele and takes them both to Cheron. When they arrive, everyone is shocked to discover Cheron is now a wasteland. Bele and Lokai are now the last of their kind. They lash out at each other, blaming the other for the destruction. To make matters worse, as they are fighting, they are cloaked in auras that contain so much energy that they might destroy the Enterprise itself. Kirk realizes he has no choice–they are too consumed by their own hatred. He lets them escape to save his ship. Lieutenant Uhura is so bewildered that she asks if this hatred is all their society ever had. Kirk ruefully answers, “No, but it’s all they had left.”
This episode is a warning to humanity. If we continue to let bigotry consume us, our planet will become like Cheron, a planet aptly named after the ferryman of Hades. It offers no quick solutions, for none exist.
Next, back to the bad as we look at how Star Trek ended–not with a bang, but with no ending at all.
Aspie Catholic 
The metaphor was a bit “too obvious” even to seven-year-old TOS-rerun-watching me, and I still wish they’d done it more subtly. Still an excellent episode.
Third season problems. I chose this to show that even the worst season had some gems.