His code name is Gary Seven. On the world where he was raised, he is known as Supervisor 194. Where that world is, only the inhabitants know - but for thousands of years these inhabitants have been taking people from Earth and training them, preparing them for a desperate mission: to save the people of Earth from their own foolish and warlike nature.
Assisting Gary Seven in his assignment on Earth are Roberta Lincoln, Earth-born, twenty-something, sometimes flighty, sometimes erratic, but with a keen mind and a high IQ; and the Beta Five computer, capable of analytical decisions and not at all shy about informing Supervisor 194 of what it views on his shortcomings.
Oh, yes - and Isis.
Star Trek: Assignment: Earth is intended to be a version of the Assignment: Earth television series that never was - taking the original episode (which was planned as a backdoor pilot to a spin-off series) as a jumping off point for a series of stories on 20th centuryEarth.