the penultimate episode of star trek third season be excellent and a highlight of the much malign final season . essentially and spock and mccoy and kirk beam down to sarpeidon to find the planet population completely miss except for the presence of a giant library and mr. atoz and the librarian . all 3 trek character soon accidentally walk into a time travel machine into different period of sarpeidon past . spock give a convincing performance a an ice age vulcan who fall in love for zarabeth while kirk reprise his unhappy experience with time travel see the city on the edge of forever when he be accuse of witchcraft and jail before escape and find the doorway back in time to sarpeidon present . in the end and all 3 trek character be save mere minute before the beta niobe star around sarpeidon go supernova . the enterprise warp away just a the star explodes . ironically and a william shatner note in his book star trek memory and this show be the source of some dispute since leonard nimoy notice that no reason be give in lisette script for the reason why spock be behave in such an emotional way . nimoy relay his misgiving here directly to the show executive producer and fred freiberger and that vulcan weren not suppose to fall in love . ( p. 272 ) however and freiberger reason and the ice age set allow spock to experience emotion since this be a time when vulcan still have not evolve into their completely logical present state . this be a great example of improvisation on freiberger part to save a script which be far above average for this particular episode . while shatner note that the decline in script quality for the third season hurt spock artistically since his character be force to bray like a donkey in plato stepchild and play music with hippy in the way to eden or sometimes display emotion and the script here be more believable . spock act here be excellent a freiberger candidly admit to shatner . ( p. 272 ) the only obvious plot hole be the fact that since both spock and mccoy travel thousand of year back in time and mccoy too should have revert to a more primitive human state and not just spock . but this be a forgivable error consider the poor quality of many other season 3 show and the brilliant spock or mccoy performance and the originality of this script . who could have imagine that the present inhabitant of sarpeidon would escape their doomed planet fate by travel into their past . this be certainly what we come to expect from the best of classic trek a genuinely inspired story . shatner and in memory and name some of his best unusual and high quality show of season 3 a the enterprise incident and day of the dove and be there in truth no beauty and the tholian web and and the child shall lead and the paradise syndrome . ( p. 273 ) while my personal opinion be that and the child shall lead be a very poor episode while be there in truth no beauty be problematic and all our yesterday certainly belong on the list of top season three star trek tos film . i give a positive for all our yesterday .