#1 ∙ S1.E2 ∙ YesteryearSat, Sep 15, 1973After finding himself erased from recent history, Spock must travel back in time to save himself as a youth.8.1/10 (1.1K)Rate
#2 ∙ S1.E5 ∙ More Tribbles, More TroublesSat, Oct 6, 1973Cyrano Jones returns, infesting the Enterprise with tribbles that now grow to monstrous size.7.0/10 (931)Rate
#3 ∙ S1.E14 ∙ The Slaver WeaponSat, Dec 15, 1973Spock, Uhura and Sulu discover an ancient multi-use weapon and are captured by the Kzinti who are equally interested in it.7.0/10 (788)Rate
#4 ∙ S2.E6 ∙ The Counter-Clock IncidentSat, Oct 12, 1974The Enterprise finds itself trapped in a 'negative universe' which causes the crew to begin to grow younger and younger toward infancy.7.0/10 (708)Rate
#5 ∙ S1.E12 ∙ The Time TrapSat, Nov 24, 1973The Enterprise and a Klingon ship are trapped in space-time warp where only their cooperation will allow them to escape.6.9/10 (755)Rate
#6 ∙ S1.E6 ∙ The SurvivorSat, Oct 13, 1973A famous humanitarian is found alive near the Romulan Neutral Zone after being missing for five years, but he may not be who he claims to be.6.8/10 (838)Rate
#7 ∙ S2.E4 ∙ AlbatrossSat, Sep 28, 1974Dr. McCoy is arrested and charged with causing an alien plague.6.8/10 (697)Rate
#8 ∙ S1.E3 ∙ One of Our Planets Is MissingSat, Sep 22, 1973The crew of the Enterprise must stop a living planet-consuming cloud before it attacks an inhabited world.6.7/10 (907)Rate
#9 ∙ S1.E15 ∙ The Eye of the BeholderSat, Jan 5, 1974While investigating the disappearance of Federation members, Kirk and his landing party find themselves placed in an alien zoo.6.7/10 (715)Rate
#10 ∙ S1.E1 ∙ Beyond the Farthest StarSat, Sep 8, 1973The Enterprise finds an ancient abandoned starship with a malevolent entity aboard, eager to take over the Starfleet ship.6.6/10 (1.1K)Rate