"Operation -- Annihilate!" is the twenty-ninth and final episode of the first season of the American science fiction television series Star Trek. Written by Stephen W. Carabatsos and directed by Herschel Daugherty, it was first broadcast April 13, 1967. In the episode, the crew of the Enterprise must find a way to exterminate behavior-altering parasites that have taken over the bodies of residents of a Federation colony, including Captain Kirk's brother, Sam, and family. Plot The USS Enterprise is tracking a path of mass insanity that has affected several planets, causing the collapse of their civilizations. They approach Deneva, a Federation colony where Captain Kirk's brother, Sam, has been stationed along with Sam's wife Aurelan and son, Peter. After entering the system, they try to stop a ship as it dives into the local sun, its pilot raving about being "free" before the ship is destroyed. Transporting to Deneva's main city, Kirk, First Officer Spock, Chief Medical Officer Dr. McCoy and a security detail find the town quiet. A group of men armed with clubs try to warn the landing party away, and then attack. Kirk has the men stunned, but McCoy finds that their brains are still being violently stimulated. The party locates the Kirk family home; Sam is dead (played by William Shatner), while Aurelan (Joan Swift) acts irrationally before passing out and Peter (Craig Hundley) is comatose. Kirk and McCoy return with the survivors to Enterprise, where McCoy finds they are suffering from a condition similar to that of their attackers. McCoy gives both painkillers, and Aurelan wakes briefly to tell Kirk of horrible "things" spreading from planet to planet, using others' bodies to build ships. Kirk returns to the planet and joins Spock in search for these entities. They find a number of single-celled creatures attached to the walls and ceiling of one building. The creatures fly, and attempt to attack the humans; the landing party finds they are nearly immune to phaser fire. One makes contact with Spock before Kirk can pry it off, and Spock falls in pain. They transport back to the Enterprise, and McCoy determines that the creature has injected some of its tissue into Spock's spinal column; it will be impossible to remove surgically. When Spock regains consciousness, he attempts to take control of the ship but McCoy sedates him in time. Later, Spock apologizes to Kirk and asserts that his