Spock travels through the Guardian of Forever to his own childhood and must save his younger self.
Spock uses the Guardian of Forever to return to his childhood on Vulcan, in order to repair a change in history. There, he meets his younger self and must help the boy face a test of survival in the desert, with his pet sehlat, I-Chaya, at his side.
Written by D.C. Fontana, the story is widely regarded as the best of the animated series. It gives a moving portrait of Spock's early life and his bond with his father, Sarek. The heartfelt treatment of loss and acceptance won the episode many admirers, and it remains a favourite of fans.