The final broadcast episode of Star Trek's second season was this clever and funny story in which the Enterprise travels back in time to 1968 (the year this program aired) to discover how the nuclear arms race came to an end. Captain Kirk (William Shatner) encounters a strange fellow named Gary Seven (Robert Lansing), who claims to have been trained by extraterrestrials in sabotaging the escalating nuclear threat. With the ambivalent aid of a nervous secretary (Teri Garr), Seven (yes, there was a Trek character with that name before Voyager) attempts to carry out his assignment, but Kirk isn't sure if he can be trusted.

One of the Star Trek time travel episodes

Fun in its self is a subset of time travel episodes, such as "Tomorrow is Yesterday", and "The City on the Edge of Forever." Or the quasi back in time episodes like "A Piece of the Action" with Spock-o.

The enterprise goes back in time to do some research. There they accidentally intercept a transporter beam. The occupants are a person named Gary Seven that claims to be a contemporary human of the time on a mission to save the earth, and a cat (maybe) that just purrs a lot.

After Gary escapes the clutches of the Enterprise, it is pretty clear that he is up to no good. This may be beyond the abilities of Spock and Kirk to believe or control but it is not beyond secretary Roberta Lincoln's (a young Terri Garr with her signature confused look) ability to figure out something is amiss.

Will Gary fulfill his mission?
Will Kirk and Spock help, hinder, or be part of the outcome?
Will Roberta find out what is be hind the purr?
Will anyone live happy ever after?

Star Trek about to go on a diet

Earth-This episode, which featured the crew returning to Earth in 1968 to observe a rocket launch, was certainly unusual. it becomes much more than an observation once they are forced to decide whether Seven's role is a positive or negative one in the prevention of nuclear war. Any viewer unaware that this was a pilot episode of a proposed spy show would be forgiven for wondering how the crew ended up in a such a mundane setting. While Robert Lansing and Terri Garr are a big step up from your average Trek guest stars, there is a reason the show was not picked up. Nevertheless, the plotline is entertaining enough to yield one quirky episode.

Tidbit: Kirk was never any rounder than he was right here; well, not until the Trek movies anyway.