Kirk leads a survey mission to a peaceful, primitive planet which he
visited 13 years before as a lieutenant. He is dismayed to see a group
of villagers armed with flintlocks, weapons they shouldn't have at
their current stage of development. The villagers ambush the landing
party and wound Spock. Returning to the U.S.S. Enterprise, Spock is put
under the care of Dr. M'Benga, who once interned in a Vulcan ward.
M'Benga tells McCoy they've done all they can for Spock, and that he
has to recover on his own.
a Klingon vessel is detected in orbit around the planet, and Kirk
orders Chekov to keep the Enterprise out of sensor range while he
returns to the surface. He'll be looking for Tyree, the tribal leader
he befriended years earlier. Minutes after Kirk and McCoy beam down in
native clothing, they are attacked by a mugato, a white apelike
creature with poisonous fangs, who bites Kirk before McCoy can kill it
with a phaser. They can't return to the Enterprise, so Kirk tells McCoy
that Tyree's people have a cure for the mugato poison.
people find Kirk and McCoy and take them to their caves, informing them
that Tyree is now their leader, and his wife, Nona, knows how to help
Kirk. But Tyree and Nona are currently on a scouting mission. Nona is
using drugs to keep Tyree devoted to her, and she urges him to acquire
"firesticks" for their people, but being a devoted pacifist, he
refuses. Informed about Kirk, Nona heads back to the caves, where she
sees McCoy using his phaser to heat some rocks. Nona is intrigued, and
wants to know more about their guests. Nona treats Kirk by cutting her
hand and pressing a mahko root against Kirk's wound. She collapses but
Kirk recovers. Now, according to legend, Kirk will be unable to refuse
on the Enterprise, Dr. M'Benga has informed Nurse Chapel that Spock is
in a state of self-induced hypnosis to heal his own injuries. When
Spock's readings fluctuate, M'Benga is pleased, and tells Chapel that
if Spock regains consciousness she is to do whatever the Vulcan asks.
Kirk and McCoy that the firesticks first appeared nearly a year ago,
but assumes the villagers have been making them — he hasn't
seen any strangers. Kirk asks him to take them to the village under
cover of dark. Nona joins them and implores Kirk to help make Tyree a
powerful man, but the captain says he will not interfere.
Kirk and McCoy into the village, where they find a forge containing
clear evidence that Klingons are involved. They watch in hiding as the
villager's leader, Apella, enters with a Klingon. Kirk and McCoy
overpower them, take a flintlock and escape with Tyree's help.
regains partial consciousness and demands that Chapel strike him. She
does so hesitantly at first, but at Spock's insistence she slaps him
harder and harder, until Scotty walks in and stops her, not knowing
he's endangering Spock by doing this. M'Benga finds out what's
happening, rushes over and slaps Spock violently until he is fully
conscious. Spock thanks him for bringing him out of his hypnotic state.
planet, Kirk teaches Tyree and his people how to fire the stolen
flintlock. McCoy points out that he is corrupting the hill people's
society, but Kirk replies that the Klingons left them no choice
— in order to bring equity back between the hill people and
the villagers, he has to provide equal weapons. McCoy is horrified, but
has no alternative solution. Realizing Tyree is hesitant to arm his
people, Kirk hopes that Nona can convince her husband to fight. When he
approaches her, she uses the same drug on him that she used to seduce
Tyree. Kirk falls under her spell. Tyree sees what's happening and aims
the flintlock at his wife, but he cannot bring himself to shoot. He
throws the weapon away in disgust and walks off.
mugato attacks Kirk and Nona. After a struggle, Kirk is forced to
destroy the creature with his phaser. Seeing her opportunity, Nona
knocks Kirk out and takes the phaser. Tyree and McCoy find Kirk and
revive him, while Nona runs into a patrol of villagers and offers them
victory by using Kirk's phaser. But the villagers attack and kill her.
Tyree and Kirk rush in and overpower the villagers. When Tyree learns
that Nona is dead he takes up the rifle and tells Kirk he needs more
weapons. McCoy retrieves Kirk's phaser, and Spock contacts them from
the ship. Kirk orders Scotty to manufacture a hundred flintlocks
— they are making serpents for the Garden of Eden.