This is a poorly conceived Classic Trek episode which was salvaged by the superior acting of the show's primary actors. Kirk beams down to the planet Gideon and finds himself on an exact duplicate of the Enterprise but doesn't realise this since the 'set up' is so convincing--even though he meets Odona, its lone occupant. Surely, Kirk should have sensed some kind of a trap immediatedly. The Enterprise crew can't locate their captain who doesn't materialize where he is supposed to--in the Gideonite council chambers--and are concerned that his life is in danger. But Spock doesn't notice at once that the beam down coordinates the Gideonites gave for Kirk is different from the ones they sent to the Enterprise to beam up a member of the Gideon council later? Any normal crewman would have quickly checked the coordinates and noticed the discrepancy between 079 and 709 and that the Gideonites have deliberately altered the numbers. Several Trek characters move out of their previous characterization with Spock and Kirk appearing less intelligent than they really are. Frankly, this is unforgivable.<br /><br />The scenes of Kirk with Odona on the empty duplicate copy of the Enterprise on Gideon also don't make much sense especially when you consider that the planet is supposed to be chronically overpopulated. The Gideon council chamber created so much free space for one man when they could have solved their overpopulation problem by having Kirk transport Odona to Dr. McCoy's sickbay for treatment? There is little logic to this show or its script. The Mark of Gideon is one of the subpar shows of season 3--not as horrendous as The Way to Eden--but still bad nevertheless. There is a memorable line which Spock says when Starfleet and its officials refuse to give him permission to beam down to Gideon and locate Kirk: "Diplomats and bureaucrats may function differently but they achieve exactly the same results." So, Spock himself has to violate a Starfleet directive to save Kirk. At least, that action was logical and highlights his loyalty to the captain. <br /><br />Odona was a wonderful actor--and a good foil for captain Kirk even though their romance has little basis in fact. I guess Kirk's libido was in overdrive in season 3 of TOS. It was not unreasonable for Odona to offer to sacrifice herself and 'die young' in order to let her civilization survive. A noble idea...even if Kirk was left with the short end of the stick by being a guinea pig who supplies a deadly virus to stop Gideon's chronic overpopulation. Most of the episode's scenes are imaginatively written if one excludes the preposterous image of hundreds of anonymous Gideonites crowding the exterior of the Gideonite Council. The touching scenes between Hodin and his dying daughter Odona was well done. Overall, Hodin, Odona, Kirk and Spock's performance elevate the show to a 4 out of 10 rating in my view--still a failure but not a total disaster. If season 3 of Star Trek had a proper film budget, the producers could have had the sets to properly depict Gideon and avoided all the numerous plot holes. Pity!