Fairest of Them All

The story begins with a recap of the last few minutes of the original episode. In the mirror universe, "our" Kirk urges mirror universe-Spock to take command of the ISS Enterprise, spare the Halkans and find a way to make peace to prevent the Terran Empire from collapsing. He and his landing party are then transported back to the Federation "prime" universe, while their "evil" counterparts return in the alternate reality.

The evil Kirk, now in command again, is determined to take the dilithium crystals from the Halkans or to destroy them as an example of what happens to those who dare to resist the Terran Empire. The Halkans are not willing to hand over the crystals and Kirk orders a torpedo barrage on their planet, rejecting a diplomatic solution recommended by Spock. The pitiless attack completely wipes out the Halkan civilization but also destroys the dilithium crystals on the planet. Spock points out that the loss of the crystals would not have happened if the Captain had followed his advice. Facing an unexpected and firm criticism by his first officer, a visibly nervous Kirk leaves the bridge and reaches his quarters.

Meanwhile, three Andorian vessels have witnessed the reckless attack to the Halkans and have communicated to the Enterprise that they will no longer recognize the authority of the Terran Empire, formalizing the start of a revolution. Spock informs the Captain of the approaching of the Andorian ships but when Kirk orders him to destroy them if they try any aggressive moves, Spock refuses to comply. Kirk reacts to the act of insubordination by activating the Tantalus Field, a deadly device concealed in his quarters, to kill Spock. Unexpectedly, the machine does not seem to work. The Captain then calls his private guards and they head to the bridge to arrest Spock.

Spock, in the meantime, has left the bridge and has convinced Scotty to join the (now explicit) mutiny. They take possession of the auxiliary control room, from where they have full control of the navigation of the ship. Other crew members, sent by Kirk to eliminate Spock, are attracted to the peaceful philosophy promoted by the Vulcan and they join the mutiny as well. Marlena reveals to Spock that she was responsible for disabling the Tantalus Field when Kirk tried to kill the first officer, but that the device could be used now to eliminate Kirk. Spock rejects the suggestion, replying that no revolution can succeed using the same methods applied by the previous one.

The more time passes, the more Kirk is abandoned by his crew and feels helpless, to the point that the Captain asks Spock to meet at the officer's lounge, to discuss the matter in a civil way and to find a compromise. Spock accepts the invitation, well aware that the meeting could hide a trap. When the two men are facing each other, Kirk tries to shoot Spock but the Vulcan reveals to the Captain that all the weapons have been disabled through a dampening field. Kirk, enraged for failing the attempt, attacks the Vulcan and during a pause in the fight shouts his thoughts about the crew, stating that they are just expendables pawns to reach his goals. Unbeknownst to him, his statements were being broadcast to the entire ship by Spock, showing the crew the real nature of their leader. Two guards then enter the officer's lounge and, to Kirk's surprise, arrest and finally neutralize him.

Spock gives a shuttlecraft to Kirk and to the few crew members still loyal to him, so that they can reach the nearest habitable system. Spock states that he's aware of the fact that the entire Terran fleet will try to stop the Enterprise and his attempts to build a peaceful Empire, but that he must try. In the last scene, Spock takes command of the bridge as Captain and gives to the navigator the order to move "forward".