Episode Title: "TOMORROW IS YESTERDAY"
Production Number: 21
Original Air Date: 01-26-67
Stardates: 3113.2, 3114.1
The U.S.S. Enterprise is en route to Starbase Nine for resupply when a black star of high gravitational attraction starts dragging the ship toward it. The Enterprise uses all its warp power in reverse to escape the black star's gravity, but the breakaway sends the Enterprise through space and time into Earth's atmosphere in the late 1960s, before the first manned Moon shot next Wednesday.
A United States Air Force pilot, Captain John Christopher, investigates the Enterprise as a U.F.O., and records its image on his jet fighter's wing camera. The Enterprise uses its tractor beam on the air craft, but it begins to break up, so the pilot is beamed aboard.
Captain Kirk and the Enterprise crew must recover Captain Christopher's flight film from an Air Force base, and find a way to return to the future without polluting the timeline. Lt. Commander Spock's research indicates that Captain John Christopher will have a son, Colonel Sean Jeffrey Christopher, who will fly the first mission to Saturn, so the Enterprise must return Captain Christopher to his proper place in history before returning to the future.
The Enterprise uses another slingshot effect, flying toward the Sun and pulling away at full power, in order to create another time warp, and while doing so, Captain Christopher is beamed back into his jet at the point in time before he spotted the Enterprise, and the Enterprise returns to its own time and makes contact with Starfleet Control.
Factoid: The U.S.S. Enterprise works for Starfleet Control, under the authority of the United Earth Space Probe Agency. There are only 12 ships like it in the fleet.
Factoid: The U.S.S. Enterprise recently went to Signet Fourteen, a planet dominated by women, for general repair and maintenance, and the inhabitants gave the Enterprise computer system an affectionate female personality.
Factoid: There are 430 crew members on the U.S.S. Enterprise.
Guest Characters: *Transporter Chief Lt. Kyle, Lt. Leslie
KEY: [brackets]=illusions *star=first appearance