that should make a good specicin. temperature's starting to drop. yeah. at night it gets down to 120 degrees below zero. that's nippy. [man shouts] [rocks sliding] [coughing] what happened? i fell off that bank, sir. cut my hand. let's see. get back to the ship. report to the sick bay.

[communicator chirping] geological technician fisher, ready to beam up. all right. locked onto you. energize. [beeping] coadjutor engagement. what happened? i took a flop. ontotohat? i don't know. some kind of yellow ore. magnetic. decontaminate that uniform. yes, sir.

[communicator signal] captain kirk readady to beam up. just one moment, captain. it checks out ok now. you better go get a synchronic meter so we can double-check. yes, sir.

are you all right, captain? yes, i'm all right. just a little dizzy. here, let me give you a hand. i can't get through there. nothing serious. wilson will be right back, sir. [beeping] space... the final frontier. these are the voyages of the starship enterprise. its five-year mission--

to seek out new life and new civilizations,

captain's log, stardate 1672.1. specimen-gathering mission on planet alpha 177. unknown to any of us during this time, a duplicate of me, some strange alter ego, had been created by the transporter malfunction. [door opens] captain? are you all right, sir? can i give you a hand, sir?

thank you. it might profit you to let dr. mccoy give you the once over. all right, engineer, i'll have my engines looked to. ship's manifests, sir. i think they're in order now. thank you, yeoman. that's all. i've checked-- yes,s,ir. ahh. [whirring] you picked a good day, fisher. business has been lousy. what'd you do, take a fall on purpose so you could get a little vacation? [door opens]

er. i have no sympathy for clumsiness. no, sir. the hand's much better, sir. what can i do for you, jim?

[knock on door] yeah? mr. spock. come in. yes, mr. spock, what is it? is there something i can do for you, captain? like what? well, dr. mccoy seemed to think that i should check on you. that's nice. come on, spock, i know that look. what is it? well, our good doctor said that you were acting like... a wild man, demanded brandy. [laughs] our good doctor's been putting you on again. hmm. well, in that case, if you'll excuse the intrusion, captain, i'll get back to my work.

captain. what is it, scotty? transporter breakdown, sir. continue circuit testing. we beamed up this animal, and... well, look for yourself. it's in this specimen case. [growling and barking] yes? a few seconds after they sent this one up through the transporter, that duplicate appeared. except it's not a duplicate. it's an opposite. two of the same animal, but different. one gentle--this. one mean and fierce-- that. some kind of savage, ferocious opposite. captain, we don't dare send mr. sulu and the landing party up. if this should happen to a man...

you startled me. is there something that you-- can i help you, captain? "jim" will do here, janice. oh. you're too beautiful to ignore.

we've both been... pretending too long. stop pretending. aah! let's stop pretending. come here, janice. don't fight me. don't fight me, janice. captain! just a minute, janice. just a minute! aah! ah... aah! ohh! ohh!

! geological technician fisher. deck 12, section-- me? my yeoman said that? i've been resting here since you left me... alone, mr. spock. captain, dr. mccoy reports that you demanded this brandy in sick bay and left with it. i found this bottle in yeoman rand's quarters. not true. i haven't been to the sick bay.

then he kissed me and he said that we-- that he was the captain and he could order me. when you mentioned the feelings we'd been hiding, and you started talking about us-- us? well, he is the captain. i couldn't just... you started hurting me. i had to fight you, scratch your face. yeoman.

. look at me. look at my face. are there any scratches? i was sure i scratched you. i was frightened. maybe-- yeoman. i was in my room. it wasn't me. sir, fisher saw you, too. fisher saw... if it hadn't been... i can understand. i don't want to get you into trouble. i wouldn't have even mentioned it. it wasn't me. it was you, sir. do you know what you're saying? yes, i know what i'm saying.

you can go now, yeoman. there's only one logical answer.

captain's log, stardate 1672.9. on the planet's surface, temperatures are beginning to drop, our landing party there in growing jeopardy.

s. how did all this happen? i don't know, sir, but when fisher came up, his suit was covered with a soft yellow ore that had highly unusual properties. it may have caused an overload. can't tell, not yet. does the transporter work at all? yes, sir, but we don't dare bring up the landing party. it might be duplicated like this animal. how long will it take you to find the trouble? can't say, sir. we just can't leave those four men down there. ark. they'll die. the surface temperature of that planet goes down to 120 degrees below zero at night. we're doing everything we can, sir. yes, i know, scotty. about your double, captain. yes, uh...yes. we'll have to find him.

on killing it. we have no previous experience, no way of knowing what would happen to you. that's right, we don't know. but the men have to be armed. the men are to be armed, with their phasers locked. i repeat, locked, on setting number one. there can't be any chance of him being killed. he's to be taken without... if the men are forced to fire... he can't be killed. how shall we explain it to them, captain? the search parties are to capture you? tell them... the search parties, captain. yes. i'll make an announcement to the entire crew, tell them what happened. it's a good crew. they deserve to know. captain. no disrespect intended, but you must surely realize

to be vulnerable in the eyes of the crew. you can't afford the luxury of being anything less than perfect. if you do, they lose faith, and you lose command. yes, i do know that, mr. spock. what i don't know... is why i forgot that just now. mr. spock. if you see me slipping again, your orders... your orders... are to tell me. understood, captain.

something has happened to me. somehow, in being duplicated, i have lost my strength of will. decisions are becoming more and more difficult. this is the captain speaking. there's an impostor aboard the ship, a man who looks exactly like me and is pretending to be me. this man is dangerous. utmost caution is to be observed. the impostor may be identified by scratches on his face. repeat. the impostor may be identified by scratches on his face. section chiefs, assign personnel to the search. all search parties report to mr. spock for assignment. something?

oh, yes, yes. all hand phasers must be set on base cycle, stunning force. the impostor is not to be injured. use minimum force. repeat... i'm captain kirk! the imposter is not to be injured. i'm captain kirk. i'm captain kirk! i'm captain kirk!

wilson! sir? wilson, give me your phaser. yes, sir. how have you been? fine, sir. kirk: how's it going down there, mr. sulu? it's already 20 degrees below zero. can't exactly call it balmy. isn't there any way we can help them? thermal heaters were transported down. they duplicated. they won't operate. then we've got to get those men up. mr. spock? spock here.

tain's cabin. he says the impostor attacked him, called him by name, took his hand phaser. acknowledged. continue the search. we'd better find him before he... but how? apparently, this double, however different in temperament, has your knowledge of the ship-- its crew, its devices. this being the case, by determining his next move. knowing how the ship is laid out, where would you go to elude a mass search? the lower levels,.

set and locked on base cycle to stun, not to kill. what about your phaser, captain? don't you think we ought to get some help, captain? no. i don't want anyone else to see the... captain, you ordered me to tell you.

you can't hurt me. you can't kill me. you can't. don't you understand? i'm part of you.

i need you. i don't need you. [electrical crackling] he'll be regaining consciousness soon, and not knowing what his physical state is, i don't think i dare give him a tranquilizer of any kind. i think we'd better bind him. yes. yes, all right.

ing from my observations, captain, you're rapidly losing the power of decision. do you have a point, spock? yes. always, doctor. we have here an unusual opportunity to appraise the human mind or to examine, in earth terms, the roles of good and evil in a man-- his negative side, which you call hostility, lust, violence, and his positive side, which earth people express as compassion, love, tenderness. it's the captain's guts you're analyzing. are you aware of that, spock? yes. and what is it that makes one man an exceptional leader? we see here indications that it is his negative side which makes him strong, that his evil side, if you will, properly controlled and disciplined, is vital to his strength. your negative side removed from you, the power of command begins to elude you.