"The Chimes at Midnight" is a story that's part of the Myriad Universes
novel Echoes and Refractions
. The story details events set in the timeline in which Spock died during childhood after being attacked by a Le-matya
, and the Andorian Thelin th'Valrass becomes Kirk's closest friend and first officer.
The story details events beginning around the time of TMP and continues through TUC. Details of Thelin's involvement during the five-year mission are sparse, but enough information is shared to suggest that the TOS portion of this timeline is similar to what happened in the primary universe. That being the case, I have to wonder what Thelin might have done to conceal his identity during "The City on the Edge of Forever" if he traveled back in time with Kirk instead of Spock. Does a timeline exist where there is a mysterious blue-skinned visitor in Earth's past?