Lincoln appears human, has no knowledge of technology past the 19th century, but is somehow familiar with the Vulcan philosophy of "Nome" (meaning "all", and showing respect for the diversity of factors making up existence).
A rock-like being with clawed hands and multiple glowing eyes atop a bulbous head, named Yarnek, announces that the inhabitants of the planet wish to conduct an experiment to determine which human philosophy is stronger: good or evil.
In this experiment, treacherous Earth warlord Colonel Phillip Green, Klingon warlord Kahless, a practitioner of unethical experiments on humanoids named Zora, and Genghis Khan, together representing evil, will be pitted against Kirk, Spock, Lincoln, and Surak (representing good) in a fight to the death.
The "good" group remain resolved that the Excalbians are the true enemy; Kirk attacks Yarnek, but the alien's body is too hot to touch.
When Lincoln arrives, he finds Surak's corpse and the waiting Kahless and Green, who fatally wound him; he staggers towards Kirk and Spock, telling them to beware, then falls dead, a spear in his back.
Kirk notes that the Enterprise may be carrying on the work of Lincoln and Surak, before the ship leaves the Excalbia solar system.
[4] This episode was released in Japan on December 21, 1993 as part of the complete season 3 LaserDisc set, Star Trek: Original Series log.3.