S01E27: The Alternative Factor
Kirk and Spock encounter an alien named Lazarus who claims to be from an anti-matter universe.
Previous Episode 
Season 1
The Man Trap
S1E1 / 08 Sep 1966
Charlie X
S1E2 / 15 Sep 1966
Where No Man Has Gone Before
S1E3 / 22 Sep 1966
The Naked Time
S1E4 / 29 Sep 1966
The Enemy Within
S1E5 / 06 Oct 1966
Mudd's Women
S1E6 / 13 Oct 1966
What Are Little Girls Made Of?
S1E7 / 20 Oct 1966
Miri
S1E8 / 27 Oct 1966
Dagger of the Mind
S1E9 / 03 Nov 1966
The Corbomite Maneuver
S1E10 / 10 Nov 1966
The Menagerie (1)
S1E11 / 17 Nov 1966
The Menagerie (2)
S1E12 / 24 Nov 1966
The Conscience of the King
S1E13 / 08 Dec 1966
Balance of Terror
S1E14 / 15 Dec 1966
Shore Leave
S1E15 / 29 Dec 1966
The Galileo Seven
S1E16 / 05 Jan 1967
The Squire of Gothos
S1E17 / 12 Jan 1967
Arena
S1E18 / 19 Jan 1967
Tomorrow Is Yesterday
S1E19 / 26 Jan 1967
Court Martial
S1E20 / 02 Feb 1967
The Return of the Archons
S1E21 / 09 Feb 1967
Space Seed
S1E22 / 16 Feb 1967
A Taste of Armageddon
S1E23 / 23 Feb 1967
This Side of Paradise
S1E24 / 02 Mar 1967
The Devil in the Dark
S1E25 / 09 Mar 1967
Errand of Mercy
S1E26 / 23 Mar 1967
The Alternative Factor
S1E27 / 30 Mar 1967
The City on the Edge of Forever
S1E28 / 06 Apr 1967
Operation: Annihilate!
S1E29 / 13 Apr 1967
Season 2
Amok Time
S2E1 / 15 Sep 1967
Who Mourns for Adonais?
S2E2 / 22 Sep 1967
The Changeling
S2E3 / 29 Sep 1967
Mirror, Mirror
S2E4 / 06 Oct 1967
The Apple
S2E5 / 13 Oct 1967
The Doomsday Machine
S2E6 / 20 Oct 1967
Catspaw
S2E7 / 27 Oct 1967
I, Mudd
S2E8 / 03 Nov 1967
Metamorphosis
S2E9 / 10 Nov 1967
Journey to Babel
S2E10 / 17 Nov 1967
Friday's Child
S2E11 / 01 Dec 1967
The Deadly Years
S2E12 / 08 Dec 1967
Obsession
S2E13 / 15 Dec 1967
Wolf in the Fold
S2E14 / 22 Dec 1967
The Trouble With Tribbles
S2E15 / 29 Dec 1967
The Gamesters of Triskelion
S2E16 / 05 Jan 1968
A Piece of the Action
S2E17 / 12 Jan 1968
The Immunity Syndrome
S2E18 / 19 Jan 1968
A Private Little War
S2E19 / 02 Feb 1968
Return to Tomorrow
S2E20 / 09 Feb 1968
Patterns of Force
S2E21 / 16 Feb 1968
By Any Other Name
S2E22 / 23 Feb 1968
The Omega Glory
S2E23 / 01 Mar 1968
The Ultimate Computer
S2E24 / 08 Mar 1968
Bread and Circuses
S2E25 / 15 Mar 1968
Assignment: Earth
S2E26 / 29 Mar 1968
Season 3
Spock's Brain
S3E1 / 20 Sep 1968
The Enterprise Incident
S3E2 / 27 Sep 1968
The Paradise Syndrome
S3E3 / 04 Oct 1968
And the Children Shall Lead
S3E4 / 11 Oct 1968
Is There in Truth No Beauty?
S3E5 / 18 Oct 1968
Spectre of the Gun
S3E6 / 25 Oct 1968
Day of the Dove
S3E7 / 01 Nov 1968
For the World Is Hollow and I Have Touched the Sky
S3E8 / 08 Nov 1968
The Tholian Web
S3E9 / 15 Nov 1968
Plato's Stepchildren
S3E10 / 22 Nov 1968
Wink of an Eye
S3E11 / 29 Nov 1968
The Empath
S3E12 / 06 Dec 1968
Elaan of Troyius
S3E13 / 20 Dec 1968
Whom Gods Destroy
S3E14 / 03 Jan 1969
Let That Be Your Last Battlefield
S3E15 / 10 Jan 1969
The Mark of Gideon
S3E16 / 17 Jan 1969
That Which Survives
S3E17 / 24 Jan 1969
The Lights of Zetar
S3E18 / 31 Jan 1969
Requiem for Methuselah
S3E19 / 14 Feb 1969
The Way to Eden
S3E20 / 21 Feb 1969
The Cloud Minders
S3E21 / 28 Feb 1969
The Savage Curtain
S3E22 / 07 Mar 1969
All Our Yesterdays
S3E23 / 14 Mar 1969
Turnabout Intruder
S3E24 / 03 Jun 1969
William Shatner
James T. Kirk
Leonard Nimoy
Spock
DeForest Kelley
Dr. McCoy
James Doohan
Scott
Walter Koenig
Pavel Chekov
George Takei
Sulu
