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Investigating the cause of a massive, galaxy-wide disruption in space, the Enterprise finds a mad scientist who claims he is being pursued by a hideous being.



In standard orbit around an iron-silica-type uncharted planet, the USS Enterprise prepares to complete its survey, when the starship is violently rocked twice and everything within sensor range suddenly "blinks", almost as if the universe is on the verge of ceasing to exist. And, in the wake of this, a man appears on the surface of the planet, where moments earlier there was no life.

Act One[]

Beaming down, Captain Kirk, Spock, and the landing party encounter a man. "You came! Thank the heavens, it's not too late!", he exclaims. Dirty and disheveled, he falls from a rock. The landing party returns to the Enterprise with him, where Kirk learns more news – the strange phenomenon drained the dilithium crystals almost completely. Still worse, Starfleet Command issues a Code Factor 1 message – invasion status. The effect experienced by the Enterprise was also experienced everywhere in the galaxy, and far beyond. Starfleet withdraws all nearby ships – Commodore Barstow informs Kirk that the Enterprise is the bait.

In his quarters, Kirk talks to his "guest" – a man named Lazarus, who is pursuing a "thing," a monster who destroyed his entire civilization. He informs Kirk that he will stop at nothing to destroy it. Beaming back down to the planet, Kirk learns from Spock that there is no other creature here. Spock, accusing Lazarus of lying, states "I fail to comprehend your indignation, sir. I have simply made the logical deduction that you are a liar." Kirk demands the truth – and the universe turns inside out once again. The same "winking" phenomenon occurs again. And Lazarus – first he has a bandaged forehead, and then he doesn't, and then he does again.

Act Two[]

Iron-silica planet onscreen, remastered

Strange energy visible on the planet on the viewscreen

Meanwhile, Spock has discovered a source of radiation that is not there – a "rip" in the universe, where regular physical laws do not apply. The key to locating this source seems to be the dilithium crystals – a revelation which excites Lazarus, who demands the impossible: that Kirk give him the crystals.

The captain refuses, but Lazarus overpowers Lieutenant Charlene Masters as well as an engineering officer and steals two dilithium crystals, nevertheless.

Act Three[]

In the briefing room, Kirk confronts Lazarus, but he denies it, blaming his monster. And the evidence suggests he isn't the thief, for the crystals are not aboard his ship. In Sick Bay, Kirk confronts Lazarus with his lies, which Lazarus explains away by claiming that he is a time traveler; his spaceship is actually a "dimensional corridor gateway"and The dead world the Enterprise orbits is the distant future of his destroyed homeworld; the place and time he has traveled to in pursuit of the monster. At Dr. McCoy's urging, the crew departs Sick Bay to allow Lazarus to rest and recover from his fall. [[ Having relocated to the briefing room to consider all of the known evidence, Kirk and Spock conclude that the strange energy must come from a source outside the universe. A source in another, parallel universe. There are two copies of Lazarus, and they are periodically exchanging places through a kind of door – and if they ever exist in the same universe at the same time, everything, everywhere, will be annihilated in a cataclysmic matter/antimatter explosion.

Meanwhile, the alternative Lazarus creates a diversion by starting a fire in main engineering, steals the ship's energy crystals, then beams down. Kirk pursues. As he attempts to enter Lazarus' spaceship, he vanishes, hurled through the corridor into the other universe.

Act Four[]

Lazarus' spaceship

Lazarus-A timeship; Lazarus-B timeship was identical except that the dome on top had been taken off

Once there, Kirk meets the other but sane Lazarus-B, and learns the truth. Lazarus-B's people discovered how to pass through the negative magnetic corridor that both connects and protects the two universes. When this happened, Lazarus-A couldn't bear the knowledge that he had a duplicate, and resolved to destroy his opposite. He is mad and doesn't care if this causes the destruction of two universes. Lazarus-B and Kirk realize he must be stopped: if Kirk can force Lazarus-A into the corridor, Lazarus-B can hold him there, and Kirk can destroy his spaceship – which will also destroy Lazarus-B's spaceship. Access to the corridor will be sealed forever and both universes will be safe, but the men named Lazarus will be at each others' throats for the remainder of eternity. Kirk goes back through the corridor and fights in hand-to-hand combat forcibly throwing Lazarus-A into the "dimensional door." Kirk then has the crystals removed from the timeship and heads back to the Enterprise, ordering Lieutenant Leslie to bring the ship's phasers to target the inter-dimensional 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. Kirk ruminates on the fact that the two Lazarus are going to be at each other's throats for all time and wonders how it would be. Spock reminds Kirk that the universe[s] are now safe. "For you and me. But, what of Lazarus? What of Lazarus?"

Log entries[]

Memorable quotes[]

"I want facts, not poetry."

- Kirk, after Spock describes the cosmic disturbances as "winking out"

"He's death! Anti-life! He lives to destroy!"

- Lazarus, on his antimatter counterpart

"I told you, it was the thing! All white, black and empty. A terrible emptiness."
"Let's get back to the ship."
"He'll kill us all if we don't kill him first! Kill! Kill! Kill!! Kill!! Kill!!!"

- Lazarus and James T. Kirk

"Are you deaf as well as blind?!"

- Lazarus, to Kirk and company

"I fail to comprehend your indignation, sir. I've simply made the logical deduction that you are a liar."

- Spock, to Lazarus

"Sometimes pain can drive a man harder than pleasure."

- Kirk to McCoy, on an injured Lazarus

"Jim, madness has no purpose or reason. But it may have a goal."

- Spock

"If they meet."
"Annihilation, Jim. Total, complete, absolute annihilation."

- Kirk and Spock, on the two Lazarus counterparts existing in the same universe

"So you're the terrible thing? The murdering monster? The creature?"
"Yes, captain. Or he is. It depends on your point of view, doesn't it?"

- Kirk and the antimatter Lazarus

"You'll be trapped inside that corridor with him forever. At each other's throats throughout time."
"Is it such a large price to pay for the safety of two universes?"

- Kirk and the antimatter Lazarus, on sealing the magnetic corridor

"Captain, the universe is safe."
"For you and me. But what of Lazarus? What of Lazarus?"

- Spock and Kirk

Background information[]

Production timeline[]


  • The original script called for a romantic entanglement between Charlene Masters and Lazarus that was eventually cut due to Roddenberry considering it too similar to the romance between Khan and McGivers in "Space Seed". As stated by Roddenberry in a Season One memo: "In both 'Space Seed' and this story, we have a crew woman madly in love with a brawny guest star and flipping our whole gang into a real mess because she is in love… do they have to do [this] in two of our scripts?" [1]
  • There is no officer played by Larry Riddle as noted among the cast for this episode in the Star Trek Concordance (1st Titan edition, p. 28). Lieutenant Larry Riddle was Charlene Masters' jealous boyfriend in the first draft of the script. [2]

Cast and characters[]

Leslie in command

The navigator and Leslie

  • James Doohan (Scott) and George Takei (Sulu) do not appear in this episode. The absence of Scotty has been remarked in several commentaries as being highly unusual, given the extensive exposure in the episode of engineering matters, such as the theft of Dilithium crystals, as well as Lazarus sneaking about engineering and attacking various engineering crew members. (Cushman, Marc, "These are the Voyages", Jacob Brown Press, 2013)
  • Curiously, in spite of a higher ranking officer serving as the navigator, this was the second episode that Leslie was seen in the command chair, and the first episode in which Eddie Paskey is credited in the ending credits, albeit misspelled as "Lesley".
  • Richard Derr, who plays Commodore Barstow in this episode, later played Admiral Fitzgerald in the episode "The Mark of Gideon".
  • Actor John Drew Barrymore (father of actress Drew Barrymore) was originally contracted to play Lazarus. Barrymore was scheduled to begin filming on the second day of production, 17 November 1966, however, the previous afternoon he sent word to the studio that he will refuse to show up to work. Barrymore's replacement, Robert Brown, on the recommendation of his friend, William Shatner, was contacted the same night, literally dragged to the studio and offered the job on the spot, starting the next morning. He recounted the filming to be very tight and tense. (These Are the Voyages: TOS Season One 1st ed., pp. 415-416)
  • The Star Trek production team filed a grievance against Barrymore at the Screen Actors' Guild, which led to him being unable to obtain acting work for six months in 1967. (Inside Star Trek: The Real Story, pp. 201-202; These Are the Voyages: TOS Season One 1st ed., pp. 415-416, 420)

Sets and props[]

Dilithium reamplification

New "recharging section" of Engineering

  • This episode introduces a new set, a small subsection of engineering, described in the final draft of the script, dated 11 November 1966, as the "Lithium [sic] Crystal Recharging Section", which was described as "A portion of Engineering where there are bins into which dilithium crystals are placed for recharging." Part of the dilithium energizer panel in the set used the same controls as the neural neutralizer from "Dagger of the Mind".
  • Although Lazarus's spacecraft resembles a flying saucer, James Blish describes it as "cone-shaped" in his novelization of the episode in Star Trek 10.
  • The dome of Lazarus' time ship was later reused to encase the Providers in "The Gamesters of Triskelion".

Costumes and make-up[]

  • Periodically throughout the episode, the two versions of Lazarus exchange places. One of them has a wound or bandage on his head which McCoy treated: this is the "insane" Lazarus from our universe; the other is his rational counterpart from the antimatter universe.
  • Although Masters is referred to as a lieutenant and works in engineering, she wears a blue uniform of the sciences section, and it has no rank stripes, which normally denotes the rank of Ensign.
  • Lazarus' costume was later worn by an extra playing a Babel Conference delegate in "Journey to Babel".


The Alternative Factor credits spelling error

The word "SCRIPT" is misspelled

  • The visual of the iron-silica planet from orbit is reused footage previously representing Alfa 177 in "The Enemy Within" and M-113 in "The Man Trap". This planet effect was reused again as Argus X in "Obsession" and Ardana in "The Cloud Minders".
  • The footage of the two Lazaruses fighting was created by filming two stuntmen fighting in a smoke-filled room with orange and purple walls, then double-exposing its color negative footage over an astronomical photograph of the Trifid Nebula. (citation needededit) By actual count Lazarus changes between the universes about eight times.
  • In the closing credits of the show, the title billing for Script Supervisor is misspelled "SCPIPT SUPERVISOR".
  • Unique to the original series are the angle of the Enterprise as it fires its phasers to destroy Lazarus's ship, as well as the use of a single phaser beam and the lack of a sound effect when the beam is viewed from space.


  • In the opening scene Spock describes the planet as having an "oxygen-hydrogen atmosphere". Such an atmosphere is practically impossible since a single spark would ignite it, perhaps even explosively.
  • This is the first time that live two-way communication with Starfleet Command is depicted. In previous episodes, communication with Starfleet Command was through delayed radio messages.
  • Depending on which version of this episode you watch, the closing stills change. The original syndicated version and the VHS version show the still as the Enterprise leaving the Earth-like planet from "Miri", however, the Sci-fi Channel and DVD version show the still as just a blue planet, possibly Rigel 12 from "Mudd's Women" or Starbase 11 from "Court Martial".


  • The Agony Booth website included this episode among "The Worst of Trek". In their recap, they write that in the episode, "very little actually happens, and what little that does comes about only because Kirk and Company are written to act in such a way that can only be described as severely brain damaged." The reviewer continues, "I never thought I'd say this, but this episode is making "Spock's Brain" look pretty goddamn good right about now!" He concludes, "this is one of the most poorly constructed fifty minutes I've ever seen. An almost impossibly incoherent script, a damp squib of a finale, and some horrible editing make this one of the true stinkers in the Trek universe." Also, he mentions that "[John Drew] Barrymore didn't show up for filming. Given the script, I can't say I blame the fellow. The rest of the cast should have done the same thing, to be perfectly frank." [3]

Remastered information[]

"The Alternative Factor" was the forty-ninth episode of the remastered version of The Original Series to air. It premiered in syndication on the weekend of 1 December 2007 and aside from the standard CGI replacement footage of the Enterprise and the planet-of-the-week, this episode also featured several new, modest effects shots of the alternative warp effect, as well as phaser and transporter effects.

The next remastered episode to air was "The Return of the Archons".

Video and DVD releases[]


Links and references[]


Also starring[]

Guest star[]



Uncredited co-stars[]

Stunt doubles[]


abrasion; accusation; all hands; "all right"; alternative; alternative warp; analysis; annihilation; answer; antimatter; antimatter universe (aka minus universe; negative universe) assistant; "at a loss for words"; "a thing"; atmosphere; bait; bandage; battle stations; being; black; blindness; body temperature; "Bones"; bruise; bull; captivity; cartographic section; censure; civilization; Code Factor 1; coffee; commodore; computer bank; computer report; constitution; container; contact; country doctor; course; creature; danger; deaf; death; devil; dilithium (aka dilithium crystal); dimension; dinosaur; dizziness; door; double-talk; drill; Earth; effect; electrical impulses; emptiness; enemy; energizer/energizing circuits; energy; eternity; evidence; existence; experimentation chamber; explosives; face; fact; Fahrenheit; fire; footprint; forehead; formula; freedom; general alert; "get to the point"; gravimetric field; gravity; guest; head; heart; heaven; Hell; hole; hour; Human (Human being); humor; hydrogen; idea; inch; indignation; information; invasion; iron; joke; justice; key; Lazarus' planet; Lazarus' planet system; Lazarus' spaceship; liar; lie; life object; life survey; living being; living creature; location; logic; "lost his mind"; madman; madness; magnetic communication satellite; magnetic effect; magnetic field; main screen; mass; matter; matter universe (aka positive universe) medic; mental state; Milky Way Galaxy; mind; minute; miracle worker; mission; monster (aka beast); movement; muscleman; negative magnetic corridor; "not hold water"; object; "of course"; orbit; ounce; "out of the question"; oxygen; pain; parallel universe; paranoia; parsec; patient; phaser bank; phenomenon; photographic section; physical law; physical makeup; physical warp; pleasure; poetry; powder keg; power; priority one; prison; pulsation phenomenon; quadrant; question; radiation; range; rationality; recuperative powers; red 2 message; report; riddle; rip in the universe; rock; safety valve; screening; search; search party; second; section; security red; security team (aka security detail); self-preservation; sense of humor; sensor; ship's physician; silica; space; spaceship; speculation; "stand by"; Starbase 200; Starfleet Command; "strong as a bull"; surface; terrain; thing; threat; throat; time chamber; time ship; time traveler; trick; truth; understatement; unit; universe; vengeance; visual section 988-TG; water; weapon; white; word; wound; year; zero gravity

Unreferenced materials[]

biological lab; chemoscientist; Riddle, Larry; rose

External links[]

Previous episode produced:
Star Trek: The Original Series
Season 1
Next episode produced:
"Tomorrow is Yesterday"
Previous episode aired:
"Errand of Mercy"
Next episode aired:
"The City on the Edge of Forever"
Previous remastered episode aired:
"The Deadly Years"
TOS Remastered Next remastered episode aired:
"The Return of the Archons"