The Enterprise's crew encounters the flagship of the "First Federation" that is crewed by an alien being, Balok, who falls prey to possibly the worst bluff in the history of bad bluffs. To escape certain death, Captain Kirk claims that the Enteprise has incorporated into it something called Carbomite, which he describes as being both a material and a device which guarantees mutually assured destruction should anyone attack them.
Just what is this supposed to mean?
And just how did this bluff work on anyone possessing more than two neurons to rub together?
It's a good thing that Harry Mudd wasn't along for this voyage of the USS Enterprise, otherwise, he probably would have introduced the people of the "FirstFederation" to poker and cleaned those suckers out and touched off an interstellar incident.
The Carbomite Maneuver is noteworthy for something else besides Captain Kirk saving the day through the use of a bluff so unbelievably that it might as well be classified as a deus ex machina. For one thing, it's one of the few episodes of Star Trek: The Original Series where the Enterprise's crew actually venture off to where no man has gone before.
It also posits that an alien civilization that is advanced enough to be capable of space-flight must also be capable of understanding and appreciating the Enterprise's mission of peace.