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
(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
[examining four stunned Denevans
There's something wrong, Jim. Their nervous systems - unconscious like this there should be just routine autonomic activity, but I'm getting a very high reading as though, even in their unconscious state, they're being violently stimulated.