The Enemy Within ( episode ) A transporter malfunction splits Captain Kirk into two people – one good and one evil , and neither capable of functioning well separately . Summary . Teaser . During a survey of Alfa 177 , geological technician slips down a rock , gashing himself badly and smearing his uniform with a strange magnetic type of yellow ore . He beam s up to the for treatment . Detecting a curious overload in the transporter circuitry , Lieutenant Commander Montgomery Scott has Fisher decontaminated before reporting to sickbay , but the problems have already begun ; the strange ore has altered the function of the transporter . Next , Captain Kirk beams up from the planet , before the fault is discovered . He apparently materializes normally and Scott escorts the disoriented captain out of the room . Kirk is , in fact , a shadow of himself . Due to this transporter accident , Kirk has been split into two beings . The first that materialized embodies all of Kirk ' s positive qualities . Moments later , after everyone has left , Kirk ' s evil twin materializes . Act One . Some time passes before the mishap is discovered . He demands Saurian brandy from McCoy in sickbay and proceeds to roam the ship ' s corridor s drunk . McCoy goes to Commander Spock about this who goes to the good Kirk about what the good doctor tells him . Kirk shrugs it off telling Commander Spock that McCoy was just pulling his leg . The evil duplicate Kirk , who was now instinctively drawn to Janice Rand , was alone with her in her quarters , drunk and amorous . The duplicate Kirk mentioned to her the feelings they ' d been hiding , claiming she was " " too beautiful to ignore , " " and " " too much woman , " " and that they have both been " " pretending too long . " " The duplicate Kirk suddenly grabbed Rand and starting kissing her very hard and rough . As she was fighting back , the duplicate Kirk pushed her to the floor and attempted to rape her , but she defended herself and left a large scratch on the duplicate Kirk ' s face . During the struggle , the evil Kirk attacks Crewman Fisher , who was walking by Rand ' s quarters . In sickbay , Rand tells the good Kirk , plus Spock , and McCoy that the captain tried to assault her in which both her and Fisher accuse him of this . Kirk firmly denies this whereupon Spock deduces that there is an impostor of him aboard the " Enterprise " . Act Two . Scotty finds that the yellow ore Fisher beamed up with somehow caused an overload in the transporter . The transporter does indeed work but they dare not use it for risk of duplicating Sulu and the rest of the landing party . Kirk tells Spock that he must inform the crew of what has happened to him , since they deserve to know . Spock , with all due respect , tells Kirk that as he is the captain , he cannot afford to be anything less than perfect in the eye s of the crew . If he does appear so , the crew will lose faith in him – and in turn , he will lose command of the " Enterprise " . Kirk knows this and wonders why he just forgot it just now . Later , on the bridge , Kirk makes an announcement to his crew from his chair about the impostor aboard . While making the announcement , his evil half is rummaging through the captain ' s quarters . Good Kirk informs the crew that the impostor can be identified by scratches on his face , and warns the crew to set the phasers for stun and must not injure the imposter . Evil Kirk angrily destroys the captain ' s desktop monitor and rants at the top of his lung s " " I ' m Captain Kirk . . . I ' M CAPTAIN KIRK ! ! ! " " Evil Kirk goes to good Kirk ' s mirror and finds make - up on the table . He applies some of it to his scratches and they are now barely visible . He opens the door to good Kirk ' s quarters and finds Crewman walking down the corridor near the room . He asks Wilson for his phaser . Wilson hands it over and is promptly knocked out . Later , both the good Kirk and Spock in the briefing room try to figure out where Kirk would go on the " Enterprise " to elude a mass search . Good Kirk quickly deduces that the evil Kirk is hiding in the lower levels of the ship – the engineering deck . He and Spock head there . In main engineering , a cat and mouse game ensues between the two Kirks and they confront each other near the warp core . Just as the evil Kirk is about to kill the good Kirk , Spock knocks him out with the Vulcan nerve pinch , but not before the phaser discharges and disables the transporter ionizer with a phaser shot , making it harder to rescue Sulu and the landing party who are trapped on the rapidly freezing planet . Act Three . Meanwhile , on the planet below , the remaining landing party is suffering through the increasingly bitter cold . Attempts to beam heaters and other support devices produce only non - functional duplicates . Kirk speaks to Sulu in the " Enterprise " s briefing room , trying to reassure his helmsman , all the while growing more and more unsure of his command abilities . Spock cuts in and tells Sulu to hold on for just a little while longer . Evil Kirk is screaming while being restrained on a bio - bed in sickbay , in pain from his body functions having been weakened from the duplication process . Good Kirk takes his evil self ' s hand , tells him not to be afraid and to use his mind , rather than his savagery . McCoy takes Kirk aside for a brandy . Kirk realizes through McCoy that he " needs " his negative side of himself back but does not want it back . McCoy assures his captain that all Humans have a dark side to them and that his strength of command lies in his negative self . Finally , Scott and Spock believe they have isolated and repaired all the damage . Spock contacts Kirk and asks him to come down to the transporter room . An Alfa 177 canine test animal , previously split , is sent through to see if it will reintegrate . Spock and Scott subdue the fierce canine with a hypospray and place it beside its good self on the transporter pad . Spock and Fisher place the two canines on the transporter pad and Scotty energizes . " " If this doesn ' t work , I don ' t know what will , " " Scotty says . The canines become one again , but it rematerializes dead from the shock from having suddenly had its two halves reintegrated forcefully . Act Four . The evil Kirk recovers in sickbay while Sulu contacts the good Kirk from the planet , just before he succumbs to the extreme cold . The good Kirk decides to release his evil half and have both of them go through the transporter , but the evil Kirk attacks and overpowers the good Kirk in sickbay and dresses in good Kirk ' s wraparound tunic . Later , heading to the bridge , the evil Kirk , pretending to be the good Kirk , runs into Janice Rand outside a turbolift and explains to her that the transporter malfunctioned , and that the animal part of him was with her in her cabin during the attempted rape . Evil Kirk ( again pretending to be the good Kirk ) also points out that the evil Kirk scratched his face to make them more alike . Arriving on the bridge , evil Kirk orders navigator Lieutenant John Farrell to take the ship out of orbit and abandon Sulu along with the landing party , callously asserting that they cannot be saved . At this point , the good Kirk appears on the bridge with McCoy . At first , Farrell and the others are confused as to which one is the good Kirk , but soon the evil Kirk collapses under the strain . " " I want to LIVE ! " " , the evil Kirk screams and cries soon before falling into his good self ' s arms . Later , both Kirks are taken to the transporter room to be reintegrated as one being . Spock handles the transporter console and promises Kirk that he will take command of the " Enterprise " if the procedure is unsuccessful . Spock energizes the transporter and the two Kirks disappear . After a few tense moments , Spock materializes Kirk back in the transporter chamber as one person . To Spock and McCoy ' s relief , the much more confident Captain Kirk steps off the pad and orders that the landing party be rescued immediately . Sulu and the others are beamed back aboard , frostbitten but alive . On the bridge , Rand awkwardly tries to explain to Captain Kirk what his imposter told her about what had happened and when she tries to elaborate further , Kirk simply thanks her and walks away . When Rand hands a PADD to Spock to sign , the first officer says to her , " " The , uh , imposter had some " interesting " qualities , wouldn ' t you say , yeoman ? " " She takes the PADD and stylus from him and walks away in a huff as Kirk orders that the " Enterprise " break orbit of Alfa 177 to continue its mission . Memorable quotes . " " Oh ! . . . Captain ! You startled me . Is there something that you . . . ? " " " " Can I help you , Captain ? " " " " Jim , will do here , Janice . " " " " Ooohhh . . . " " " " You ' re too beautiful to ignore . Too much woman . " " " " We ' ve both been . . . pretending too long . " " " " You can ' t afford the luxury of being anything less than perfect . If you do , they lose faith , and you lose command . " " " " I ' m Captain Kirk . I ' M CAPTAIN KIRK ! ! ! " " " " And what is it that makes one man an exceptional leader ? We see here indications that it ' s his negative side which makes him strong , that his evil side , if you will , properly controlled and disciplined , is vital to his strength . " " " " If I seem insensitive to what you ' re going through , captain , understand : it ' s the way I am . " " " " Do you think you might be able to find a long rope somewhere and lower us down a pot of hot coffee ? " " " " I ' ll see what we can do . " " " " Rice wine will do if you ' re short on coffee . " " " " Any possibility of getting us back aboard before the skiing season opens down here ? " " " " He ' s like an animal . A thoughtless , brutal animal . And yet it ' s me . Me ! " " " " We all have our darker side . We need it ! It ' s half of what we are . It ' s not really ugly . It ' s Human . " " " " The intelligence , the logic . It appears your half has most of that . And perhaps that ' s where man ' s essential courage comes from . " " " " He ' s dead , Jim . " " " " Being split in two halves is no theory with me , doctor . I have a Human half , you see , as well as an alien half , submerged , constantly at war with each other . Personal experience , doctor . I survive it because my intelligence wins over both , makes them live together . " " " " The animal part of me came to your cabin . He even scratched me to make us look more alike . I ' d like a chance to explain it to you . You don ' t mind if I come to your cabin later ? " " " " No , sir . " " " " Can half a man live ? " " " " I want to live ! " " " " I ' ve seen a part of myself no man should ever see . " " " " The . . . impostor had some . . . interesting qualities , wouldn ' t you say , yeoman ? " " Links and references . References . abort control circuit ; Alfa 177 ; Alfa 177 canine ; alter ego ; autopsy ; " base cycle , stunning force " ; body function panel ; " Bones " ; burnout ; cabin ; casing ; circuit s ( bypass , leader , main ) ; coadjutor engagement ; coffee ; decontamination ; ; dizziness ; Earth ; engineering ; exposure ; frost ; frostbite ; full postmortem ; geological technician ; hand phaser ; hotline ; impulse engine ; leader circuit ; logic ; magnetism ; make - up ; microtape s ; mirror ; name ; neck ; ore ; overload ; pot ; protoplaser ; power generator ; rape ; rice wine ; room service ; rope ; Saurian brandy ; search party ; section chief ; ship ' s manifest ; shock ; skiing ; specimen case ; surface temperature ; survival training ; synchronic meter ; thermal heater ; training program ; tranquilizer ; transporter ; transporter circuit ; transporter technician ; transporter unit ionizer ; vacation ; velocity balance ; Vulcan nerve pinch ; willpower