When the Enterprise is assigned to observe Earth's history in 1968, suddenly it intercepts a transporter beam which originates at least a thousand light-years from Earth, bringing aboard a humanoid alien 'agent Gary Seven' holding a black cat called Isis, who warns them to step back and let him go to accomplish his mission to save Earth; initially phaser-struck down, he manages to beam himself away, actually on a mission to prevent a nuclear rocket being launched at McKinley base because earth is socio-politically not ready for its technological progress. He assumes a classified identity to override a powerful computer, and mistakes the wrong girl, Miss Lincoln, for another agent; the computer reports both other agents he seeks are deceased in an accident. Meanwhile Kirk and Spock beam down to investigate if the alien isn't hostile, realizing the risk of changing their own past. When they get on his trail, the girl sees Spock's ears, calls the police and Seven gets away; they must ... Written by
Did You Know?
This episode features one of the first uses of stock footage of the first test launch of the Saturn V moon rocket, which occurred just the preceding November (1967). See more
When launch control announces that the rocket has reached 1,000 feet, it is shown already deviating from the vertical on a downrange trajectory. This does not happen until the rocket is much higher than that. Since the Saturn V is 365 feet tall, at an altitude of 1,000 feet, it is less than three times its height above the ground, and does not appear to be at a great height in relative terms. Furthermore, if the rocket had deviated that far from the vertical at only 1,000 feet, it probably would have crashed. See more
Captain James T. Kirk
Captain's log. Using the light speed breakaway factor, the Enterprise has moved back through time to the 20th century. We are now in extended orbit around Earth, using our ship's deflector shields to remain unobserved. Our mission - historical research. We are monitoring Earth communications to find out how our planet survived desperate problems in the year... 1968.