The Enterprise has been ordered to go to a planet that is being terraformed into new planet. For some odd reason, the planet has been ignoring contact from the Federation and they need to investigate. When the Captain contacts the base's leader (Walter Gotell), he is very evasive and unfriendly and it's obviously he does NOT want them coming to the planet's surface. Once there, it's obvious SOMETHING is up, as a laser seems to come to life on its own and kills one of the workers. Then, it tries to kill Data. Someone or something is controlling the laser--and Picard is determined to investigate further. Eventually the root cause is discovered--and inorganic life form! Gordi and Data bring the small speck-like being to the ship for examination--and soon it begins to grow, refuse to stay in containment and takes control of the computer systems. Obviously it IS intelligent. And, obviously the leader of the base was trying to create a new planet by destroying the inorganic life form--which clearly violates the Prime Directive.
In many ways, this episode reminds me of one from the original "Star Trek" series--the one where miners inadvertently are killing the eggs of an inorganic creature, the Horta. Here, the entity is of a much different form but the concept is quite similar. Overall, a very interesting episode and one that manages to be entertaining despite a very simple idea and a very non-traditional alien!