Yesteryear

Kirk and Spock return from observing the past through the Guardian of Forever to find that nobody recognises Spock. An Andorian, Thelin, is now first officer, and the records show that Spock died on Vulcan aged seven during the kahs-wan, a survival ordeal in the desert. Spock remembers being saved at that age by a cousin called Selek and realises that the cousin must have been himself. He travels back through the Guardian and, posing as Selek, meets his younger self: a boy bullied for being half human and under pressure from his father Sarek. When young Spock heads into the desert to prove himself, Selek follows and helps rescue him from a le-matya, but the boy's beloved pet sehlat, I-Chaya, is fatally poisoned defending him. Young Spock chooses to let I-Chaya die peacefully rather than prolong his suffering. With his future secured, Spock returns to the restored timeline.