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?
When Spock stuns the creature to take as a specimen, it lands face down, but close-ups show it face up. See more
Unusual eye arrangement. I might've known he'd turn up something like that.
What's that, doctor?
I said, please don't tell Spock I said he was the best first officer in the fleet.
Why thank you, Dr. McCoy.
You've been so concerned about his Vulcan eyes, Doctor, you forgot about his Vulcan ears.