Four-and-a-Half Vulcans

To help the pre-warp Tezaarians repair their failing nuclear power system without breaking Federation law, Pike, Chapel, Uhura and La'An are transformed into Vulcans, leaving four and a half Vulcans aboard when Spock is counted. The mission succeeds, but the four decide to stay Vulcan, and their new logic soon causes trouble. Pike becomes obsessively efficient, Chapel drops friendships and relationships to focus on work, and Uhura manipulates Beto into a mind meld. La'An develops warlike, almost Romulan instincts, and Scotty and Kirk team up to stop her. When Pike calls Captain Batel's return to Starfleet's judicial department illogical, she loses her temper. With help from Doug, a Vulcan who knows about katras, Spock connects with their spiritual essences and persuades them to become human again. They apologise for their behaviour, and Vice Admiral Pasalk, impressed by Batel's outburst, offers her a promotion to head the judicial department.