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?
This is the second of three times the Enterprise encounters another Constitution-class starship with the entire crew dead. The other two were in "The Doomsday Machine" and "The Tholian Web". See more
Dr. Carter's shirt is a lightened olive color during his last log entry right before his death, but when Kirk looks down at his crystallized remains, the shirt is definitely a light blue. See more
One of them lies.
But which one? If we should kill good, then evil would be among us.