A mission turns several officers into Vulcans, and Spock must reverse their altered personalities.
Pike, Chapel, Uhura and La'an are transformed into Vulcans and choose to remain that way. Pike becomes obsessed with efficiency, Uhura mind-melds with Beto to test their compatibility, Chapel cuts off her friendships and her relationship with Korby, and La'an turns into a sinister, Romulan-like warmonger. Meanwhile, Batel's request to return to her Starfleet post is rejected, and she clashes with Pike and Pasalk.
Scotty and Kirk team up to stop La'an, and Spock restores the four crew members' katras, after which they make amends with those they hurt. Pasalk then offers Batel a promotion. The comedy inverts Spock's usual struggle by giving the humans a taste of Vulcan logic taken to extremes while Spock must guide them back, and Chapel's experience leaves effects that surface again in the fourth season. Jordan Canning directed.