OFFICIAL SYNOPSISWhile visiting the recently discovered planet Phylos, the U.S.S. Enterprise landing party discovers an apparently abandoned city. While exploring the city Sulu picks up a plant and is poisoned. As the landing party tries to save Sulu, the alien species that inhabit the planet approach and save Sulu's life. Upon further investigation of the alien creatures, who are plantlike beings called Phylosians, the crew discovers that the poison that affected Sulu was accidentally brought to the planet by a visitor who subsequently worked to find a cure. The Phylosians call this visitor "Master" and "Savior."
party eventually discover that this visitor was actually a
Terran scientist by the name of Dr. Starros Keniclius who
has since died. Now a giant clone of Dr. Starros Keniclius,
by the name of Keniclius Five, has taken his place. The
giant wishes to clone Spock to create an intergalactic
peacemaker. Ignoring Kirk's insistence that the Universe has
become a virtually peaceful conglomeration of worlds,
Keniclius Five clones Spock, crippling the Vulcan almost to
the point of death. Kirk realizes the only way to save Spock
is to recite aspects of Vulcan philosophy on life and death
to Keniclius Five. Kirk convinces the clone that the new
Spock is but a copy and not the original. The clone Spock
saves the other's life through a Vulcan mind meld and the
duplicate remains on the planet with Keniclius to revitalize
that world's civilization.