The Enterprise traces a virus-like outbreak that seems to be traveling in a direct line across a planetary system. The next planet is home to Kirk's brother Sam, his sister-in-law and their young son. The Enterprise arrives too late however for Sam. They find flying jellyfish-like creatures that attach themselves to humans. They take over the victims nervous system forcing them to bend to their will. Spock finds a weapon to use against the creatures but it leaves him hopelessly blind. Written by
Did You Know?
Stock footage of Leslie's hands from Star Trek: The Alternative Factor
(1967) is used to represent the personnel in the satellite control room. This shot was removed from the remastered version of the episode. See more
(at around 10 mins) There is a person moving in and out of the frame way behind the action during the outdoor sequence. See more
I did it! It's finally gone! I'm free! I'm...