Synopsis:

A large delegation of diplomats is to be transported to a conference concerning the admission of Coridan to the Federation.   The Enterprise is carrying them, including Spock's father Sarek, when they are accosted from within and without.   Now there is a mystery to solve, a ship to fight, and Sarek is in danger of losing his life.

Wow, talk about multi-threading.   Few shows can carry this many threads and conclude them all at the end without resorting to some contrived mumbo jumbo but this one does.   Who ever wrote this one did a fantastic job.    This episode allows us to look a little more into the Vulcan psyche.  It is hard to realize now, with more than 25 years of Star Trek behind us, how little we really knew about the Federation and the aliens that made it up.  

The addition of numerous other alien species as well as the intrigue make this episode stand out from the rest.   It isn't as good as some by my personal tastes but I cannot think of one that was better written.