Air date: 1966-09-08

Runtime: 50 min

Kirk and his crew are at deadly risk from an alien creature that feeds on the salt in a human body and can take on any form.

Air date: 1966-09-15

Runtime: 51 min

Charlie Evans, the sole survivor of a transport crash, is transferred to the Enterprise from a different ship. Why are they so eager to rid themselves of him, though? There's more to Charlie than meets the eye...

Air date: 1966-09-22

Runtime: 51 min

While exploring the edge of the galaxy, the Enterprise encounters an energy barrier that gives some crewmen strange powers.

Air date: 1966-09-29

Runtime: 51 min

A strange alien substance causes the crew to lose their inhibitions.

Air date: 1966-10-06

Runtime: 50 min

A transporter malfunction causes Captain Kirk to split into his "good" and "evil" selves, and a landing party will freeze to death if they don't merge the two back together.

Air date: 1966-10-13

Runtime: 50 min

The Enterprise picks up a intergalactic conman, Harry Mudd, and three incredibly beautiful women who harbor a dark secret.

Air date: 1966-10-20

Runtime: 50 min

Nurse Christine Chapel is reunited with her old fiance on Exo III, but the scientist has plans for Captain Kirk and the Federation.

Air date: 1966-10-27

Runtime: 50 min

Kirk and a landing party are stranded on a planet due to a disease that causes any adult to die a painful death, and must deal with the local children who have survived.

Air date: 1966-11-03

Runtime: 50 min

Kirk investigates an experimental facility for holding prisoners and finds a sinister scheme.

Air date: 1966-11-10

Runtime: 50 min

The Enterprise encounters a vast alien ship that threatens the Enterprise with destruction.

Air date: 1966-11-17

Runtime: 49 min

Spock kidnaps his former captain, the crippled Christopher Pike, and heads for a quarantined planet, putting his career and Kirk's life on the line.

Air date: 1966-11-24

Runtime: 50 min

Spock's court-martial continues as he attempts to justify his abduction of Pike, the theft of the Enterprise, and his heading for a planet declared forbidden by Starfleet.

Air date: 1966-12-08

Runtime: 50 min

Kirk is one of the last survivors who can identify a mass killer, who lurks among a Shakespearean troupe aboard the Enterprise.

Air date: 1966-12-15

Runtime: 50 min

Kirk pits the Enterprise against an invisible spaceship testing the Federation's defenses.

Air date: 1966-12-29

Runtime: 50 min

The Enterprise crew take shore leave on a peaceful, pastoral planet... where their dreams and fantasies come to life.

Air date: 1967-01-05

Runtime: 50 min

Spock commands a stranded away team when their shuttlecraft is stranded on a planet with hostile natives.

Air date: 1967-01-12

Runtime: 50 min

The Enterprise finds itself at the mercy of a seemingly omnipotent being who fancies himself an 18th century Englishman.

Air date: 1967-01-19

Runtime: 51 min

When a mysterious alien race destroy an Earth colony, the Enterprise pursues, but Kirk and the alien captain are forced to fight each other by powerful aliens.

Air date: 1967-01-26

Runtime: 50 min

In a freak accident the Enterprise is sent back to 20th century Earth, and must find their way back without changing history.

Air date: 1967-02-02

Runtime: 50 min

Captain Kirk's career is at stake when he is put on trial for the loss of a crewman during an ion storm.

Air date: 1967-02-09

Runtime: 50 min

The Enterprise encounters a seemingly peaceful civilization run by a "benevolent" being named Landru... who intends for them to join his people.

Air date: 1967-02-16

Runtime: 50 min

The Enterprise picks up a crew of genetic supermen from the 20th century... and their leader, Khan, plans to create a new empire.

Air date: 1967-02-23

Runtime: 50 min

The Enterprise arrives at a planet to establish diplomatic relations and finds itself in the middle of a "peaceful" war that threatens to destroy the ship.

Air date: 1967-03-02

Runtime: 50 min

The Enterprise crew try to rescue colonists from deadly radiation, but instead encounter strange alien spores that seem to offer paradise.

Air date: 1967-03-09

Runtime: 50 min

Kirk investigates a series of grisly murders on a mining planet that are the work of a seemingly hostile alien creature.

Air date: 1967-03-23

Runtime: 50 min

The Federation and the Klingon Empire teeter on the brink of war as Kirk investigates Organia, a humble planet, inhabited by pacifists, that is unwittingly caught in the middle.

Air date: 1967-03-30

Runtime: 51 min

Kirk and Spock encounter an alien named Lazarus who claims to be from an anti-matter universe.

Air date: 1967-04-06

Runtime: 50 min

Kirk and Spock must travel into the past in order to correct a change that will alter history.

Air date: 1967-04-13

Runtime: 50 min

Kirk and the Enterprise must combat parasitic aliens threatening the lives of millions.