
PUBLICATION: Bantam Books, February 1970
CREATORS: James Blish
STARDATE: 4011.9 - 4205.5 (Season 3)
PLOT: While the Enterprise is way on the other side of the Klingon Empire, the Federation loses contact with Organia and the Klingons start a new war. Months away from the action, the crew attempts the impossible - creating a tachyon duplicate of Mr. Spock with the transporter and sending it instantaneously to Organia to see what's happening. Something goes wrong, however, and a duplicate of Spock is create, one that proves to be a traitor to Starfleet. The ship takes the long way to Organia while one of the Spocks locks himself away and both demand the death of the other. When they reach Organia, it is surrounded by a thought-reflecting field with which the Klingons have isolated the Organians. The duplicate Spock escapes to it while the ship encounters Klingon resistance. The duplicate Spock figures out how to use the field projector to affect the planet's environment and he fights the real Spock in a surreal battle, but loses and is destroyed. The crew then helps the Organians destroy the field, and the godlike beings stop the war and isolate the Klingons from the rest of normal space-time.
CONTINUITY: First real mention of Joanna McCoy, the doctor's daughter, in any media (Blish had access to the original script of The Way to Eden in which she would have appeared). Both the Organians - including the very same council members - and the Klingons - including Kor - first appeared in Errand of Mercy. Koloth and Korax (The Trouble with Tribbles).
DIVERGENCES: McCoy's nickname is Doc instead of Bones, apparently the editor's fault. Janice Rand is still aboard - possible, but not borne out by onscreen evidence. Kirk wears an Academy class ring which has never been seen on the show. The Klingons are ruled by a Grand Senate. If the Organians did indeed trap the Klingons in some kind of time loop for a thousand years, it didn't take.
SCREENSHOT OF THE WEEK

Comments
But the Organians fell off the face of the universe soon thereafter for the Trek timeline to make sense.
Seeing as how it worked out in the end (see The Undiscovered Country), I could live with that solution.