Star Trek TOS: All Our Yesterdays

There is a major plot hole in this episode, mainly why does Spock regress from going back in time while Bones remains the same but this can easily beoverlooked as this is certainly one of the best episodes from the third season. Great lines, well acted and you just have to love Mariette Hartley in her tundra hunter gear! Surprised the ice cave didn't melt around her from the heat she was throwing off. The counter story involving Kirk is also interesting, in fact, there is so much going on here you wonder how they jammed it all into one hour.