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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When Spock stuns the creature to take as a specimen, it lands face down, but close-ups show it face up. See more
[Spock, infected, beams down to the planet to collect a specimen
Jim, that man is sick - and don't give me any damnable logic about him being the only man for the job.
I don't have to, Bones. We both know he is.