The 39th episode of Gene Roddenberry’s science fiction series Star Trek premieres on NBC. Jane Wyatt and Mark Lenard guest star as Spock’s parents in their first appearance in the Star Trek mythology (in fact, their only appearance prior to the animated series or the movies, despite the characters’ prominence), and Kirk gets into a knife fight trying to salvage interplanetary diplomacy. This episode’s depiction of Vulcan/Andorian unease would become a significant element of the later Star Trek TV spinoff Enterprise. 
Stardate 3842.3: Delegates from several worlds are welcomed aboard for a trip to Babel where a Federation summit will take place, among them Vulcan Ambassador Sarek – Spock’s father, from whom he has been alienated since childhood. Spock’s human mother, Amanda, can’t stop trying to bridge the gap between her husband and son, while Spock and Sarek can’t seem to do anything but continue their rivalry. When a hidden assassin begins to kill some of the delegates, Spock – out of logic, of course – points Sarek out as a potential suspect. But Sarek suffers a heart attack just as an alien ship begins to attack the Enterprise. Kirk is stabbed by the assassin, and Spock must choose between offering some of his blood to save Sarek’s life and assuming command of the Enterprise in the emergency.
written by D.C. Fontana
directed by Joseph Pevney
music by Gerald FriedCast: William Shatner (Captain James T. Kirk), Leonard Nimoy (Mr. Spock), DeForest Kelley (Dr. Leonard McCoy), James Doohan (Mr. Scott), George Takei (Lt. Sulu), Nichelle Nichols (Lt. Uhura), Jane Wyatt (Amanda), Mark Lenard (Sarek), William O’Connell (Thelev), Majel Barrett (Nurse Chapel), John Wheeler (Gav), James K. Mitchell (Josephs), Reggie Nadler (Shras)
Notes: Though Sarek doesn’t appear in any more episodes of Classic Trek (unless one wishes to count Mark Lenard voicing the character in the animated episode Yesteryear), he appears in nearly every Kirk-era Star Trek movie after Star Trek II and makes two guest appearances in Star Trek: The Next Generation (Sarek and Unification Part I), and, played by James Frain, in the first two seasons of Star Trek: Discovery. Jane Wyatt reprises the role of Amanda in Star Trek IV: The Voyage Home; though Amanda appears in Yesteryear as well, she was voiced by Majel Barrett for that appearance. In the early seasons of Star Trek: Discovery, Amanda is played by Mia Kershner.
LogBook entry by Earl Green