It's obvious that this episode is based on various terrorist organizations of the day--such as the IRA and PLO. This isn't surprising, as all the Star Trek franchises have a history of making episodes with contemporary parallels.
In this episode, the Enterprise is visiting the Ruthian planet--a place which has been plagued with terrorist attacks for many, many years. It seems that the Ensatan separatists want their own homeland and they seem willing to do just about anything to bring about this change--including kidnapping Dr. Crusher. But there is another reason for taking her prisoner, as the Ensatans are experiencing serious genetic damage due to their use of dimensional shifting--a practice long abandoned by the Federation since it will eventually kill those who use it.
Naturally the Enterprise want the Doctor back but they also don't want to be picking sides or get pulled into the conflict. Unfortunately, the Ensatans don't see it that way and soon are targeting the Enterprise and its crew.
Overall this is a decent episode, though some might be offended at the moral relativity. In other words, terrorists and those fighting them in this one are basically the same. This is sometimes true...sometimes not in real life. But its message is compelling nevertheless.
