The Devil in the Dark ( episode ) The " Enterprise " arrives at Janus VI , where an unknown monster is destroying machinery and killing the miners , threatening the entire mining operation . Summary . Teaser . On Janus VI , a miner named Schmitter replaces at his guard post . Schmitter is extremely nervous about doing guard detail , but Chief Vanderberg reassures him by recommending that he have his phaser on him at all times and if he hears or sees anything , help can arrive in three minutes . Moments after Chief Vanderberg and the other guards move on , they hear a scream and return to find Schmitter reduced to a pile of ashes . Act One . Two days later , the arrives at Janus VI in response to the distress call . For the past three months , a creature has been terrorizing the mining colony , killing more than fifty people , sabotaging machinery on the lower levels , and bringing the pergium production to a halt . Captain Kirk , Spock , and McCoy analyze the situation in Vanderberg ' s office . Only one man saw the creature and lived : Chief Engineer Ed Appel , who shot it with his phaser type - 1 with no effect . He doubts that the power of a starship will do any good " down in the tunnels . " McCoy analyzes Schmitter ' s remains ; they are not burned but corroded , as if he had been immersed in a vat of extremely corrosive acid . Spock is fascinated by a silicon sphere on Vanderburg ' s desk ; Vanderburg says there are millions of them underground but they have no value . Their conversation is interrupted by an alarm at the colony ' s nuclear reactor . The creature has killed the guard outside , burned its way in , and taken the reactor ' s main circulating pump , without which the reactor will go super - critical and irradiate half the planet . Act Two . Scott reports from the " Enterprise " that he can rig up a replacement with " some odds and ends " that might last 48 hours . Kirk orders him to beam down with it and hopes that , within that time , the original pump can be retrieved . Spock , still contemplating Vanderburg ' s sphere , speculates that they may be dealing with a silicon - based lifeform rather than carbon - based life . This would explain why the creature does not show up on sensor s and why it was impervious to Appel ' s phaser . Kirk summons Lieutenant Commander Giotto and a security team , and Spock adjusts their type 2 phaser s to be more effective against silicon . The security team is dispatched to level 23 , which was opened just before the attacks began . Kirk orders them to set their phasers to maximum , and to fire whether or not attacked . A security officer is by the creature , bringing Kirk and Spock to the scene . They see the creature , and fire on it , damaging it , but it gets away , tunneling through the rock with its acid . They examine a piece of the creature , which seems to prove Spock ' s theory of silicon - based life . Spock detects only one such creature within a hundred miles , and suggests that to kill it would result in the extinction of the species , " " a crime against science , " " he states . Kirk says there is no alternative . Act Three . The search teams focus on where the creature was seen . Spock gives them orders to " " surround it , and possibly capture it " " but Kirk countermands him , stressing that the goal is to " " shoot to kill . " " Kirk orders Spock away to assist Scott with the reactor , but Spock counters with logic and Kirk relents . Spock states that the probability of he and Kirk both getting killed by the creature is approximately " 2 , 228 . 7 to 1 , " to which Kirk ultimately allows Spock to stay with him . Scott ' s improvised pump fails and Kirk prepares to beam the miners up to the ship . But Vanderburg and his men refuse to be chased from the planet ; they vow to fight the creature – " with clubs " if there are not enough phasers . Kirk and Spock separate and Kirk finds a chamber with hundreds of the silicon spheres . Spock warns Kirk not to damage them but is still not ready to state his theory about them . A roof near Kirk collapses , which Spock finds much too odd to be a coincidence . The only way out for Kirk is to continue forward – to a face - to - face encounter with the creature . Act Four . Kirk senses the creature ' s intelligence , as it backs off when Kirk raises and lowers his phaser and it displays its wound from the previous encounter , and Kirk ' s determination to kill the creature softens . Spock arrives and initiates a Vulcan mind meld to communicate with the creature . He learns that it is a sentient being of a race called the Horta and is in extreme pain , and the Horta learns enough to etch the ambiguous " NO KILL I " into the rock floor . Kirk summons McCoy , though Spock thinks his medical training will be useless on the Horta . Another mind meld reveals that the Horta is preparing for the extinction of its race . It directs the Human s to find their pump in the " Chamber of the Ages . " Kirk tells Spock to communicate to the creature that they are trying to help . He goes to the Chamber and finds about a million silicon spheres , which Kirk and Spock now understand are Horta eggs , ready to hatch . But several miners , held apart from the confrontation by the " Enterprise " security team , overpower it and stream into the confrontation . Kirk vows to kill the first man who fires and explains that the Horta is a mother reacting naturally to the destruction of thousands of her children . Spock adds that the Horta " harbor ill will towards no one . " Kirk envisages a collaboration between the miners and a new generation of Horta who can tunnel through rock with as much ease as they do walking through air . McCoy repairs the Horta ' s wound by troweling thermal concrete , used mostly for the construction of emergency shelter s , onto it . The crew returns to the " Enterprise " and Vanderberg radio s in that the Horta have started hatching and have already found new mineral deposits . He even mentions that one can get used to their appearance . Spock says the Horta told him the same thing about Humans . He counters some teasing from McCoy by replying that the Horta especially admired Vulcan ears . Memorable quotes . " " When that creature appears , men die . " " " " Kiss it ! Baby it ! Flatter it if you have to ! But keep it going . " " " " Mr . Spock , we seem to have been given a choice : death by asphyxiation or death by radiation poisoning . " " " " There ' s nothing more dangerous than a wounded animal . " " " " Either one of us by himself is expendable . Both of us are not . " " " " Pain ! Pain ! " " " " No kill I . What is that ? A plea for us not to kill it ? Or a promise that it won ' t kill us ? " " " " I ' m a doctor , not a bricklayer ! " " " " You ' re a healer . There ' s a patient . That ' s an order . " " " " By golly , Jim ! I ' m beginning to think I can cure a rainy day ! " " " " The Horta has a very logical mind . And after close association with Humans , I find that curiously refreshing . " " " " I suspect you ' re becoming more and more Human all the time . " " " " Captain , I see no reason to stand here and be insulted . " " Background information . Remastered information . Max Gabl was responsible for creating the new CGI for the mining colony , at the time it was his very first assignment on the episode . Producer Niel Wray was included in the matte shot as one of the two workmen walking into a tunnel in the lower corner . Wray and another member of the team were shot against a blue screen and placed into the matte . Niel was chosen because he fit into the costume . Links and references . References . 50 , 000 years ago ; 53rd century ; 2210s ; 2240s ; 2247 ; 2266 ; acid ; adit ; administrative head ; animal ; Altar of Tomorrow ; armor plating ; asbestos ; asphyxiation ; bandage ; bone ; " Bones " ; bricklayer ; carbon life ; cerium ; Chamber of the Ages ; Channel 1 ; chief ; chief engineer ; chief processing engineer ; chemist ; club ; colony ; devil ; distress call ; drift ; ear s ; egg ; empathy ; Federation ; ; gallery ; generation ; geology ; ghost ; gold ; graph ; guard ; hatchery ; healer ; Horta ; Janus VI ; Janus VI colony ; life span ; logic ; main circulating pump ; maintenance engineer ; medical kit ; mile ; miner ; mineral ; " modus vivendi " ; monster ; nuclear reactor ; oxygen ; pergium ; pergium production station ; phaser bank ; phaser I ; phaser II ; physician ; plant physician ; physiology ; platinum ; plumber ; pound ; PXK pergium reactor ; quota ; radiation poisoning ; rain ; reactor room ; retardation mechanism ; science ; sentry ; silicon ; silicon - based lifeform ; silicon nodule ; starship ; ; subsurface chart ; teeth ; thermal concrete ; tissue ; trace element ; tricorder ; trowel ; tunnel ; uranium ; Vault of Tomorrow ; volcano ; Vulcan ; Vulcan mind meld ; uranium ; yard ; zoology