Lieutenant Commander Gary Mitchell was a Starfleet officer aboard the U.S.S. Enterprise in 2265, one of the ship's helmsmen, and a friend of its captain James T. Kirk. When the U.S.S. Enterprise was searching for the SS Valiant's last known position, Gary Mitchell was exposed to the energies of a barrier at the edge of the Milky Way, where they found the ship. Exposure to the energies gave him ESP and altered his personality.