The Enterprise travels to the planet Janus 6 to assist the mining colony there. Kirk, Spock and McCoy beam down to the planet where Chief Engineer Vanderberg tells of a creature loose in the mine tunnels killing some of his men. The monster seems to appear out nowhere then disappears just as quickly. Finding that the creature, known as a Horta, lives in a newly opened part of the underground mining complex, Spock uses the Vulcan mind meld to determine why it is killing the miners. Written by
Did You Know?
When deciding which of two tunnels to investigate, Kirk tells Spock to take the one on the left, and he'll take the one on the right. But he gestures with his phaser to the exact opposite tunnels. See more
Captain, there are literally thousands of these tunnels in this general area alone. Far too many to be cut by the one creature in an ordinary lifetime.
Then we're dealing with more than one creature, despite your tricorder readings, or - we have a creature with an extremely long lifespan.
Or, it is the last of a race of creatures which made these tunnels. If so, if it is the only survivor of a dead race, to kill it would be a crime against science.