Star Trek: Season 3, Episode 18

3 - 18: The Lights of Zetar

A mysterious storm has inflicted heavy - perhaps irreparable - damage on the library planetoid Memory Alpha. And it seems to have a curious affiliation with new crewmember Myra Romaine. As the Enterprise pursues the hazard, Romaine falls more under its influence, and the crew learns is is not a storm at all, but a form of life that means to survive at ANY cost.