The Alternative Factor


"The Alternative Factor"
Star Trek: The Original Series episode
Episode no.Season 1
Episode 27
Directed byGerd Oswald
Written byDon Ingalls
Featured musicAlexander Courage
Cinematography byJerry Finnerman
Production code020
Original air dateMarch 30, 1967 (1967-03-30)
Guest appearances
  • 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 Cadiente - Security Guard
  • Eddie Paskey - Lt. Lesley
Episode chronology
← Previous
"Errand of Mercy"
Next →
"The City on the Edge of Forever"
Star Trek: The Original Series (season 1)
List of episodes

"The Alternative Factor" is the twenty-seventh episode of the first season of the American science fiction television series Star Trek. Written by Don Ingalls and directed by Gerd Oswald, it first aired on March 30, 1967.

In the episode, the crew of the USS Enterprise encounters a "reality jumping" madman. It is the first Star Trek episode to deal with a parallel universe.[1]


The USS Enterprise is rocked by an energy pulse. Science Officer Spock informs Captain Kirk that the gravity pull of the planet fluctuated to zero and the surrounding space momentarily "winked" out of existence. Sensors locate a human presence on the planet that was not there before. Spock and Kirk beam down to the planet and find a one-man spacecraft. A disheveled man named Lazarus appears and slips off a cliff. He 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. 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.

Lazarus periodically fades in and out of the universe, encountering a lookalike enemy in a "dimensional corridor", creating an energy wink. Spock reports a "rip" in space and time on the planet. Lazarus says 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 it on his nemesis.

Kirk beams back to the planet with Lazarus and a security team to seek this 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 enemy destroyed his civilization in the past, for which Lazarus has chased him for centuries. Mr. Spock develops a hypothesis that Lazarus's enemy is his counterpart from an anti-matter universe. If he and his anti-self contact each other within either physical universe outside the dimensional corridor, they would 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. Kirk is teleported to the anti-matter universe, where he meets the Anti-Lazarus. The Anti-Lazarus admits to stealing the Enterprise's dilithium. He informs Kirk that his people believed two universes existed, and when his matter counterpart learned about it, he went insane and became obsessed with destroying him. He tells Kirk that only by destroying the ship with the two Lazaruses inside the dimensional corridor which links the two universes can both universes be saved. Kirk realizes this would trap the two men in the corridor forever.

Kirk confronts the matter 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 inside the dimensional corridor as phaser beams vaporize the ship.


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.[2]

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.[3] A ranking of every episode of the original series by, placed this episode 77th out of 79 episodes.[4] In 2017, Den of Geek ranked this episode as the 6th worst Star Trek episode of the original series.[5]

In 2016, CNET ranked "The Alternative Factor" as the ninth worst episode of all Star Trek, based on rankings between an audience and discussion hosts at a 50th anniversary Star Trek convention in Las Vegas.[6]


  1. ^ Eugene Myers; Torie Atkinson (2009-07-08). "Star Trek Re-watch: "The Alternative Factor"". Retrieved 2020-10-27.
  2. ^ Herbert Solow, Robert Justman (1997). Inside Star Trek The Real Story. June: Simon & Schuster. pp. 201–202. ISBN 0-671-00974-5.
  3. ^ Handlen, Zack (April 17, 2009). ""Errand Of Mercy" / "The Alternative Factor"". The A.V. Club. Retrieved March 2, 2010.
  4. ^ Blauvelt, Christian (2013-05-18). "Ranking All 79 'Star Trek: The Original Series' Episodes from Worst to Best". Retrieved 2019-06-08.
  5. ^ "The 15 Best Worst Episodes of Star Trek: The Original Series". Den of Geek. 2017-09-16. Retrieved 2021-01-13.
  6. ^ Kooser, Amanda. "10 worst Star Trek episodes, according to the fans". CNET. Retrieved 2020-01-19.

External links

  • "The Alternative Factor" at
  • "The Alternative Factor" at IMDb
  • "The Alternative Factor" at Memory Alpha (a Star Trek wiki)
  • "The Alternative Factor" Review of the remastered version at
  • "The Filming of the 'Alternative Factor'" excerpt covering production difficulties with episode