9/8/1966. The Man Trap — When a landing party beams down to an archaeological dig for a routine evaluation, one member of the party turns up dead under mysterious circumstances.
9/15/1966. Charlie X — The Enterprise provides transport for 17-year-old Charlie Evans, an adolescent who grew up alone on a deserted planet, and who holds powerful abilities that were key to his survival.
9/22/1966. Where No Man Has Gone Before — Kirk's longtime friend and fellow officer Gary Mitchell develops astounding superhuman powers, eventually turning him against his own captain and shipmates.
9/29/1966. The Naked Time — Members of the Enterprise crew contract a virus that has intoxicating side effects, leading some to exhibit bizarre and dangerous behavior.
10/6/1966. The Enemy Within — A transporter malfunction creates a duplicate version of Captain Kirk ... a version who dons a nasty disposition.
10/13/1966. Mudd's Women — The Enterprise rescues galactic scoundrel Harry Mudd and his hypnotically attractive passengers from a critically damaged cargo ship.
10/20/1966. What Are Little Girls Made Of? — Brilliant scientist Dr. Roger Korby takes Kirk and Chapel hostage, revealing his hopes to replace humanity with emotionless androids.
10/27/1966. Miri — The Enterprise encounters a planet that is an exact duplicate of Earth, but where all children die of a terrible disease as they approach adulthood.
11/3/1966. Dagger of the Mind — Kirk takes on an investigation into the methods of Dr. Tristan Adams, a penal colony administrator who is using unique technology to control and terrorize his patients.
11/10/1966. The Corbomite Maneuver — In uncharted space, the Enterprise encounters a mysterious alien probe. When Kirk is forced to destroy it, he incites a conflict with powerful aliens.
11/17/1966. The Menagerie, Part I — For unknown reasons, Spock seizes control of the Enterprise and sets a course for the forbidden planet Talos IV, which he had previously visited on a mission with former Enterprise captain Christopher Pike.
11/24/1966. The Menagerie, Part II — As Spock faces court martial and possible execution for forcing the Enterprise to Talos IV, the mystery surrounding Captain Pike and the Talosians is slowly revealed.
12/8/1966. The Conscience of the King — Kirk comes face to face with a criminal from the past when he learns that a political leader responsible for putting thousands to their death may be part of an acting company for which he is providing transport.
12/13/1966. Balance of Terror — The Romulans, virtually unheard of since Starfleet was at war with them a century ago, are detected by the Enterprise to be in violation of the neutral zone, possibly testing new military technology.
12/29/1966. Shore Leave — Members of the crew beam down to a world where their thoughts are magically manifested into reality.
1/5/1967. The Galileo Seven — During a shuttle mission, Spock's first command becomes a struggle of logical decisions when the team becomes stranded on a desolate planet.
1/12/1967. The Squire of Gothos — The Enterprise crew is forced to be the guests at a party hosted by a powerful, playful, temperamental being.
1/19/1967. Arena — Kirk and the captain of a Gorn ship, which had recently destroyed an Earth outpost, are forced to battle to the death to save their crew from certain destruction.
1/26/1967. Tomorrow Is Yesterday — The Enterprise is hurled back in time to the 1960s, where they become the center of a U.S. Air Force pilot's UFO investigation.
2/2/1967. Court Martial — Kirk faces trial for taking improper action that led to the death of a member of his crew.
2/9/1967. The Return of the Archons — The crew investigates a strange world where the people are locked in a collective-minded zombie-like trance, at the will of a leader named Landru.
2/16/1967. Space Seed — The Enterprise discovers an Earth ship that has been adrift since the late 1900s, and learns its warlike crew is still alive, having spent 200 years in suspended animation.
2/23/1967. A Taste of Armageddon — A landing party beams down to a planet that is locked in a simulated war with one of its neighboring worlds ... a war where deaths are tallied but actual destruction is avoided in order to prevent society from crumbling into ruins.
3/2/1967. This Side of Paradise — Having beamed down to a planet to investigate the fate of a Federation research team, members of the crew become enraptured in "paradise" when they come in contact with happiness-inducing plant spores.
3/9/1967. The Devil in the Dark — A mining colony urgently requests Kirk and his crew to stop a deadly monster that has been running rampant through the mines and killing men.
3/23/1967. Errand of Mercy — With imminent war between the Federation and the Klingons approaching, Kirk attempts to negotiate a protection agreement with a planet caught in the middle of the dispute.
3/30/1967. The Alternative Factor — Investigating a strange spatial phenomenon, a landing party discovers Lazarus alone on a planet, and learns of a dual inner-torment apparently at war within himself.
4/6/1967. The City on the Edge of Forever — The crew makes the awesome discovery of a time portal, but a demented McCoy—suffering from an inadvertent medication overdose—jumps into Earth's past and radically alters history for the worse. Kirk and Spock follow McCoy through the portal to undo the damage.
4/13/1967. Operation—Annihilate! — Alien life seizes control of a Federation colony and its inhabitants, leaving the Enterprise as the possible last defense from a species of parasitic invaders.