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
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This takes place in 2267. 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
[holding a beaker of tentacle tissue
Evidently, when the creature attacks it, uh, leaves a stinger much like a bee or a wasp, leaving one of these in the victim's body, and it takes over the victim very rapidly, and the entwining is far, far too involved for conventional surgery to remove.