Agent 347 was an agent for a mysterious race of aliens who took it upon themselves to safeguard the universe, working on planet Earth in the 20th century. In 1968 Agent 347 and partner Agent 201 were to meet with fellow agent Gary Seven, but was killed in an automobile accident before this meeting could take place. (TOS episode: "Assignment: Earth")

Theses agents were decendents of Humans abducted thousands of years ago, and genetically engineered to accomplish the goals of the Aegis. These agents would then covertly move to prevent Humanity from destroying or harming themselves. (TOS novel: The Eugenics Wars: The Rise and Fall of Khan Noonien Singh, Volume 1)