What are Little Girls Made of?

The Enterprise arrives at planet Exo III to learn the fate of Doctor Roger Korby, the ``Pasteur of archaeological medicine''. On board is Nurse Christine Chapel, Korby's fiancee, who has given up a bio-research career on Earth to find him. Korby contacts the Enterprise, and confirms that he is living in underground caverns he discovered while he was suffering from sever frostbite five years before. At Korby's request, only Kirk and Christine beam down, The doctor shows them ancient machines that were left behind by the long-dead Exoites and tended by Ruk, a giant android. Korby's aides, Dr. Brown and young Andrea, are revealed as androids and Korby fashions an android duplicate of Kirk. His intention is to take the Enterprise and ``seed'' the universe with androids. When Korby vaporizes Ruk, Kirk argues that the androids are neither peaceful nor human. Korby himself, transformed into an android, disputes this at first. When Korby realizes that he is more machine than man, he turns a phaser on himself and Andrea, Spock arrives with a landing party moments later; Nurse Chapel announces that she is staying with the Enterprise crew.