Operation: Annihilate! - Plot

Plot

Stardate 3287.2: The Enterprise is tracing a path of mass insanity that is destroying civilizations in a straight line through the galaxy, jumping from planet to planet. The next planet in line is Deneva, and Captain Kirk has Communications Officer Lt. Uhura open a hailing frequency on a private transmitter. As they enter the system, they detect a ship heading for the sun. The pilot raves incoherently until he suddenly becomes lucid… just as his ship is destroyed by the heat. Chief Medical Officer Dr. McCoy notes that Kirk's brother Sam has a laboratory on the planet where he and his family live.

Kirk takes down First Officer Spock and others in a landing party and find that the locals are strangely quiet, until a group of men come out. They try to warn the landing party away but then come after them in a fit of violence. The landing party stun them but McCoy determines that they're being violently stimulated even when unconscious. They hear a scream from the laboratory and run there to find Kirk's sister-in-law Aurelan trying to keep something from entering through the ventilator grille. They also find Sam Kirk, dead, and his son Peter unconscious.

Back on the ship, McCoy determines Aurelan and Peter are both in extreme pain and is forced to tranquilize them. Aurelan has a greater resistance and they bring her around enough for her to reveal that "they" came eight months ago, forcing a ship's crew to bring them. The more she tries to answer, the more pain she suffers. Aurelan reveals that "they" are spreading, forcing the Denevans to build ships to spread further. Before she can say anything further, she dies from the pain.

Kirk beams down to join the landing party and search for the creatures responsible. Inside a building they find pancake-sized single-celled organisms that are highly resistant to phaser fire. They try to retreat but one of them attacks Spock. They pry it off but Spock is immobilized with pain.

They take him back to the ship where McCoy determines that the creature injected something into Spock. The doctor has no choice but to call off the surgery: the creature has infiltrated Spock's spinal column with pieces of living tissue that are impossible to completely remove through surgery. Nurse Chapel still thinks Doctor McCoy should try something, and attempts to refuse when he orders her to close Spock up. McCoy threatens to get another nurse, so she submits.

In Sickbay, Spock revives and storms off to the bridge, but Chapel sees him leave and prepares a sedative, then follows him. He tries to take control of the ship. The crew are barely able to restrain him, and Chapel shows up with the sedative just in time. McCoy administers it to Spock. Back in Sickbay under heavy restraint, Spock awakens and asserts that as a Vulcan he can control the pain. Kirk orders him to be confined for a while longer to see if he can maintain control. Once they leave, Spock snaps his restraints and goes to the transporter room. He orders Chief Engineer Scott to beam him down but, following captain's orders, the engineer refuses. Spock then attacks them but Scott is able to hold him at phaser point and call the captain. Spock explains to Kirk and McCoy that the pain is gone and he has to capture one of the creatures, and he is the logical choice since he is already infected. Kirk agrees and a Denevan attacks Spock when he arrives on the planet. Spock renders him unconscious and returns to the building where they found the organisms. He stuns one of the creatures and takes it back to the ship.

In the laboratory with McCoy and Chapel, Spock determines the creature is part of a hive mind that has come from a different universe, with different physical properties, and is all but immune to phaser fire. Kirk orders them to find something that will kill the creature without destroying the host, but McCoy comes up with nothing and the captain admits that he will have to destroy the planet and everyone on it rather than let the creatures spread.

Remembering that the man piloting the Denevan ship called out that he was "free" right as the ship was destroyed by the sun, Spock and McCoy test the creature against numerous properties of the sun, to no avail. Kirk realizes that the one property they haven't tried is light. They come up with a plan to place satellites in orbit and have McCoy test the specimen they have. The light destroys the specimen but Kirk wonders if it will work on an infected victim. Spock volunteers and enters the test chamber, and is exposed to the extreme light. Spock reveals that he is free of the creature, but entirely blind. Nurse Chapel comes in to reveal that only high-end (ultraviolet) light waves were necessary, not the blinding white light that McCoy also used. Spock's blindness was ultimately unnecessary if Nurse Chapel's information had come sooner.

The Enterprise distributes the satellites and then energizes them, and the creatures are destroyed and the Denevans recover. Later, Kirk files a message to Starfleet when Spock arrives on the bridge, back to normal. Spock explains that the blindness was temporary, and that Vulcans have a second, inner eyelid to protect against the bright Vulcan sun (Spock claims that Vulcans tend to ignore the extra eyelid much as humans ignore their appendix, perhaps explaining why he did not immediately realize the blindness was only temporary). A relieved McCoy reluctantly admits he thinks Spock is the best first officer in Starfleet and Spock, with his superior Vulcan ears, overhears him, much to the chagrin of McCoy.