Yesteryear starts off rather abruptly on a planet capable of letting users pass through time with the help of a vortex-like being. As Spock & Kirk return from a trip into the past, it is established that the future has been changed and Spock is no longer remembered by any of the crew.
Performances for this episode from the regular actors remain top-notch with Nimoy proving to be more than capable of playing the leading role in the animated series. There are some minor problems with the performances here and there, but luckily nothing too distracting.
The story is as fascinating and well written as it is important to the history of Spock and his species. Even though we hardly get a good view upon the Spock’s city, what we do see is fantastically animated and represented on-screen, especially for 1973.
Overall, Yesteryear is a highly enjoyable and significant episode of Trek history with brilliant character development, story-telling and animation. If you see one anmated episode of Trek, it should probably be this.