As the Enterprise approaches planet Omega IV, they find another starship, the U.S.S. Exeter, in orbit. Kirk, Spock and McCoy beam aboard to find the ship abandoned but strewn with uniforms and crystals. The last log entry from the ship's surgeon tells them they have been infected with a deadly virus brought aboard from a returning landing party. Kirk's party beams down to the planet's surface and finds there is one Exeter survivor: Captain Ron Tracey. He has apparently ignored the Prime Directive and has taken sides in a local dispute supporting the Kohms against their arch-rivals, the Yangs. As McCoy tries to find a cure for the virus, Spock and Kirk try to make sense of the situation. They eventually realize there is an odd parallel with Earth's own history. Written by
Did You Know?
In the adaptation of this episode done for the ViewMaster (3-D) slides, the Yangs were renamed the Meraks. See more
Early on, when Kirk is calling from the Exeter's engineering section to the rest of the ship, we see various shots of different parts of the ship. One of those shots is of an empty engineering deck, which makes no sense - that is where he is calling from. See more
[about the Yangs
Animals, who happen to look like us. Still think the Prime Directive's for this planet?
Captain James T. Kirk
I don't think we've a right or the wisdom to interfere, however a planet is evolving.