mental discipline can control the pain, but that he must return to the surface to acquire a specimen to study. Kirk and McCoy agree, and Spock, on return to the colony, is able to stun a creature. Returning to the Enterprise, Spock and Kirk determine that the creatures are part of a hive mind. Spock and McCoy fail in their attempts to destroy the creature. Kirk holds a senior staff meeting, asserting they must find a solution before the creatures reach the next inhabited planet, holding over a million people; a solution that does not kill the hosts. Kirk recalls the ship's pilot stating that he was free before diving into the sun, and suspect the sun's properties may harm the creatures. He realizes that they have not tried visible light as a means to defeat the creatures. An initial test of blinding light results in the death of the specimen in sick bay. Spock then volunteers to be exposed to intense light, without eye protection, to prove that a creature infecting a host can be killed. Though the test is successful, Spock is now blind. Analysis of the initial test shows that only ultraviolet light was necessary to kill the creature. The Enterprise floods the colony with ultraviolet light from an array of satellites, killing the creatures on the planet and purging the parasites from the survivor. As the Enterprise prepares to leave orbit, Spock reveals that his Vulcan inner eyelids had prevented permanent blindness and that he can see again. Production The script, which was written by Steven W. Carabatsos, was originally titled "Operation: Destroy". Aurelan was a Denevan woman in love with a man named Kartan, and it was Kartan who flew the ship into the Denevan sun in the cold open sequence. Aurelan's father was also a major character in the teleplay, and the two colonists were not infected by the "Denevan neural parasites". Instead, they helped Dr. McCoy and Mr. Spock with the research into how light could destroy the parasites. The script did not originally end with the Enterprise crew using light to destroy the parasites. Instead, the ship learns the location of the aliens' home world, and destroys the central controlling "brain" located there. Author James Blish used this draft of the script when adapting the episode for print, and this ending appears in the chapter "Operation -- Annihilate!" in the anthology Star