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?
The actual building where Spock is attacked by the parasite is now a cafeteria belonging to Northrop Grumman Aerospace. See more
When Spock stuns the creature to take as a specimen, it lands face down, but close-ups show it face up. See more
Captain's log, stardate 3289.8. I am faced with the most difficult decision of my life. Unless we find a way to destroy the creatures without killing their human hosts, my command responsibilities will force me to kill over a million people.