The Alternative Factor

"The Alternative Factor"
Star Trek: The Original Series episode
Episode no. Season 1
Episode 27
Directed by Gerd Oswald
Written by Don Ingalls
Featured music Alexander Courage
Cinematography by Jerry Finnerman
Production code 020
Original air date March 30, 1967 (1967-03-30)
Guest appearance(s)
  • Robert Brown - Lazarus
  • Janet MacLachlan - Lt. Charlene Masters
  • Richard Derr - Commodore Barstow
  • Christian Patrick - Transporter Chief
  • Arch Whiting - Assistant Engineer
  • Tom Lupo - Security Guard
  • Ron Veto - Security Guard
  • Vince Calenti - Security Guard
  • Eddie Paskey - Lt. Leslie
Episode chronology

"The Alternative Factor" is a first season episode of the original science fiction television series, Star Trek. It is episode #27, production #20, and was broadcast on March 30, 1967. The episode was written by Don Ingalls, and directed by Gerd Oswald.

In this episode, the crew of the USS Enterprise encounters a "reality jumping" madman. This is the first Star Trek episode to deal with a parallel universe.


The Enterprise, completing a mapping assignment, is rocked by an energy pulse. Science Officer Spock informs Kirk that the gravity pull of the planet fluctuated to zero and says that the surrounding space seemed to momentarily "wink" out of existence.

Sensors locate a human presence on the planet that wasn't there before. Mr. Spock and Kirk beam down to the planet and find a one-man spacecraft. A disheveled, bearded man appears and accidentally slips off a cliff. The man survives the fall but is injured, and Kirk has him beamed to the Enterprise for examination.

Back on the ship, Lt. Masters informs Captain Kirk that the mysterious disturbance has drained the dilithium crystals in the warp drive. A message from Starfleet reports that every quadrant has been subjected to the same winking effect and electronic disruption as the Enterprise. Starfleet fears that the disruption may be a prelude to an invasion and has ordered all ships except the Enterprise to leave the area. Kirk is ordered to find the cause of the disturbance, alone.

Lazarus frequently fades in and out of the universe, encountering his nemesis in a dimensional corridor, creating an energy wink, rippling through the universe. Spock reports a "rip" in space and time on the planet. Lazarus insists that his enemy, trying to destroy the universe, is causing the phenomenon. Lazarus demands dilithium crystals so he may fix his ship and continue to fight his enemy. Kirk refuses; Lazarus steals dilithium from the Enterprise and is caught. Lazarus denies the theft and blames the theft on his yet unseen nemesis.

Kirk beams back to the planet with Lazarus and a security team to seek this "hidden" enemy. Lazarus has another "dimensional corridor" episode and is returned to sickbay. Lazarus explains to Kirk that he is a time traveler; the planet below was once his home world. Lazarus claims his nemesis destroyed his civilization in the past, for which Lazarus has chased him for centuries.

Mr. Spock develops a hypothesis that Lazarus's nemesis is actually an "anti-Lazarus", possibly from a parallel dimension; if Lazarus and his anti-self contact each other within either physical universe outside the dimensional corridor, they would destroy each other and annihilate both the matter and anti-matter universes.

Lazarus slips away from sickbay and creates a diversion in engineering to acquire dilithium. With the stolen crystals, he beams down to the planet to repair his ship. Kirk follows, but Lazarus activates his time machine just as Kirk tries to stop him. Stepping into the portal, Kirk is accidentally teleported to the other anti-dimension where he encounters the anti-Lazarus.

Anti-Lazarus calmly admits to stealing the Enterprise's dilithium. He informs Kirk that his people thought that two universes exist in which attempts to prove it, caused their destruction. Anti-Lazarus tells Kirk that only one Lazarus can exist in one universe simultaneously. Lazarus's time traveling ship is the "dimensional door," and connects both Anti-Lazarus and Lazarus; only by destroying the ship with the two Lazarus inside "dimensional corridor" which links the universes can both universes be saved.

Kirk confronts Lazarus, and pushes him into the "dimensional door." Kirk heads back to the Enterprise, ordering the ship's phasers to target the dimension ship. The two Lazaruses meet once more and fight as phaser beams vaporize the ship, sealing the two for all of eternity, caught together between universes.


John Drew Barrymore was originally cast as Lazarus, but on the morning filming began he was nowhere to be found. The part had to be quickly recast with Robert Brown. The producers filed a grievance with the Screen Actors Guild, which suspended Barrymore's membership for six months as a result, preventing him from working as an actor during that time.[1]

The special effects for the extra-dimensional "winking" episodes were achieved by superimposing a moving photograph of the Trifid Nebula over the action.


Zack Handlen of The A.V. Club, 42 years after its initial debut, gave the episode a 'C-' rating, describing the plot as "baffling" and "unrewarding" and poorly paced.[2]


  1. Herbert Solow, Robert Justman (1997). Inside Star Trek The Real Story. June: Simon & Schuster. pp. 201–202. ISBN 0-671-00974-5.
  2. Handlen, Zack (April 17, 2009). ""Errand Of Mercy" / "The Alternative Factor"". The A.V. Club. Retrieved March 2, 2010.
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