Obsession ( episode ) A survey of Argus X brings the " Enterprise " crew in confrontation with a vampiric cloud that killed a crew Kirk was on years ago , captained by the father of an ensign currently assigned to the ship . Summary . Teaser . Captain James Kirk , Spock , Ensign Rizzo , Leslie , and a security guard are carrying out a survey of Argus X , a planet rich in tritanium , a material twenty times ( 21 . 4 according to Spock ) harder than diamond . While appraising the material , Captain Kirk notices a sweet odor , and orders Rizzo and the security guards to perform a sweep with their tricorders of the perimeter of the landing site , with special instructions to scan for dikironium , and to fire on any gas eous clouds they might encounter . He notifies chief engineer Scott , standing by on the ship , that he is conducting an investigation of the area , in spite of the fact that the expects the " Enterprise " to rendezvous with them in eight hours time . Rizzo and the security team report in when they encounter an odd cloud , and are ordered to fire on it immediately . Contact is then lost with the team . When Kirk and Spock run over to them to investigate , they find two of the security team dead , and Rizzo badly injured . Every red blood had been drained from their bodies . Act one . Rizzo is quickly returned to the ship for treatment . Chief medical officer McCoy reports that Rizzo remained unconscious for some time , following massive blood transfusions . His autopsy of the deceased crewmen reveals that all red blood cells had been drained from their bodies , without any marks , cuts or incisions of any kind . Captain Kirk suggested that McCoy examine the record tapes of the , which listed casualties eleven years earlier from identical causes . At this point , Kirk decides to investigate the officers ' deaths further , in spite of the fact that the was scheduled to pick up highly perishable medical supplies from the " Yorktown " , supplies that are badly needed on the planet Theta VII . He further requests that McCoy revive Ensign Rizzo for questioning , which he does with cordrazine . Although half - conscious , and , in McCoy ' s medical opinion , unreliable , Rizzo reports that he remembered a sickly sweet odor and that he felt an intelligence when attacked . Kirk then leaves sickbay , requesting McCoy ' s medical report as soon as possible . Kirk meets with Spock on the bridge , where Lieutenant Uhura reports an urgent message from Starfleet which is promptly ignored by the captain . Because sensor scan s for dikironium were negative , Spock hypothesizes that the creature might be able to change its molecular structure and thus avoid detection from the " Enterprise " s sensor scan s . Kirk then receives word from Uhura that Ensign Rizzo had died . Ensign , the new security officer , arrives on the bridge and expresses interest in pursuing the creature that killed Rizzo , as he was close to the late ensign , having graduated from the Academy together with him . Kirk , Garrovick , and a party of four armed security officers beam down to the planet to investigate the phenomenon that killed Rizzo , with their phasers set on disruptor effect . They split into two parties of three , one led by Kirk ( with Swenson and Bardoli ) , the other by Garrovick . Kirk gives orders that the cloud was to be shot on sight . Garrovick ' s party almost immediately encounters the cloud . While it was approaching them , the cloud appeared to hover briefly ; Garrovick hesitates for an instant before firing . By the time he shoots , the cloud was moving . He missed the cloud entirely , and it attacked and rendered unconscious the two crewmen that were accompanying him . Act two . When the landing party returns to the ship , one of the men is in critical condition , and the other is dead . Kirk is now convinced that not only was the creature intelligent , but it was also the same creature which attacked and decimated the crew of the " Farragut " eleven years previously . Kirk , Spock , and McCoy meet with Garrovick in the ship ' s briefing room to hear his report . He details his experiences , including his hesitation before firing . As punishment , Captain Kirk has him relieved of all duties and confined to quarters , an action McCoy finds to be too harsh on the young man . Kirk dismisses McCoy ' s words and then directs Spock and the doctor to make any observations in official reports . He hastily leaves . At this point , chief engineer Scott reports that the " Enterprise " will be ready to leave orbit in half an hour . Kirk replies that they would not be leaving orbit , whereupon Scott reminds Kirk of the urgent nature of their mission to Theta VII . Kirk dresses Scott down , complaining that he was " tired of my senior officers conspiring against me . " When pressed , he admits that he should not have used the word " conspire " . He also severely admonishes acting science officer Ensign Chekov , who reports that they have conducted full scanner probes twice on the planet . Kirk yells at him to continue running scans twenty times if necessary until the gaseous creature was found . At this point , Spock approaches Doctor McCoy to consult on what he has observed to be a persistent , single minded fixation on the creature on the part of Captain Kirk . Spock informs McCoy that eleven years earlier , then Lieutenant Kirk , under the command of Captain on the " Farragut " , had encountered a similar situation . Captain Garrovick was the father of the ensign of the same name . Act three . Shortly thereafter , Doctor McCoy meets with Captain Kirk in his quarters to discuss his recent actions . He speaks of the terrible stress of a young officer in his first real danger , but when Kirk snaps that punishing Ensign Garrovick was " his " command decision , McCoy reveals that the " young officer " he referred to had actually served aboard the USS " Farragut " – Lieutenant James T . Kirk , assigned to phaser control . McCoy reminded him that , as a young man , " he " had hesitated before firing on the creature , causing him to miss it . Shortly thereafter , it had killed two hundred crewmen , including Captain Garrovick . McCoy suggests that Kirk ' s guilt was causing him to become obsessed , and that he was preparing a medical log entry on Kirk ' s emotional condition . Such a log requires a witness of command grade , so McCoy produces such a witness : first officer Spock . As per regulations , Spock and McCoy inquire about his recent command decisions . Kirk defends his position by stating that he had sensed that the creature was intelligent , and that he felt it was the same one that attacked them on Argus X . Since this indicated the creature was dangerous and capable of space travel , Kirk had decided to pursue it . At this point , McCoy decides to withhold his judgment on Kirk ' s emotional state . Chekov reports that scanners detected the cloud was heading into space , so Kirk orders the " Enterprise " to follow it and has the ship set on red alert . The cloud ' s speed surpassed warp eight ; if the ship traveled at that speed for a prolonged period , it would damage the engines . After a brief hesitation , Kirk decides to abandon pursuit and the " Enterprise " slows to warp six . As he could not leave his cabin , Nurse Chapel brings Garrovick his dinner . She finds him lying on his bed consumed with guilt over his inability to fire his phaser at the creature in time . When he insists he ' s not hungry , she claims that McCoy had her bring a microtape containing a simple order : to eat . She threatens to feed him intravenously in sickbay if he does not ; unknown to him , this was a ruse , as Chapel ' s tape contained " A Survey on Cygnian Respiratory Diseases " . After she leaves , Garrovick angrily throws the cover to his plate across the room , causing his ventilation control to jam . A red alert is then declared over the ship ' s intercom by Kirk , with an order for all crew to get to battle stations . Garrovick leaves his room and reports to the bridge in violation of orders . The red alert was called due to the fact that the creature had decided to turn toward the ship . With Garrovick watching , the captain orders phasers to fire on it ; however , the phaser attack is completely ineffectual , as is a barrage of photon torpedo es . The creature then enters the ship through an impulse engine vent that had been left open for repair . It enters the ship ' s ventilation system , killing one crewman and severely injuring another in the process , and leaving the crew of the " Enterprise " with only two hours of remaining air supply . Act four . Ship ' s senior officers Kirk , Spock , Scott , and McCoy meet in the briefing room to discuss the situation . McCoy feels , more than ever , that the situation was a result of Kirk ' s obsession , but Spock counters that the question of obsession is now an academic one , as the creature had attacked . McCoy is taken aback by the scientifically - inclined Vulcan ' s use of the word " creature , " the same description as the " obsessed " Human , so Spock responds that this attack – it had significantly changed its course to face the ship – indicated to him that it was , in fact , intelligent . The consensus of the meeting is that radioactive waste should be flushed into the ventilation system to drive out the creature . After the doctor and engineer leave to return to their posts , Spock also reminds Kirk that , as phasers were ineffective , there was no basis for his self - recrimination due to his actions on the " Farragut " – though the captain responds that he was not the crew member who needed to hear that message . Later , Spock visits Ensign Garrovick in his stateroom . He informs him that his hesitation was natural , which Garrovick doesn ' t want to hear , but they are soon interrupted by the sickly smell of the cloud creature , coming through the vent . Spock ejects Garrovick from his cabin , seals the door , and attempts to reverse the vent , which is jammed . From outside Garrovick ' s cabin , Kirk orders that the pressure inside be reversed . Garrovick lets the captain know that Spock had saved his life , but when he claims that he was the one who should be dead , Spock emerges from Garrovick ' s quarters and informs Kirk that neither of them died , the reverse pressure was effective and the vent was closed . When a stunned Kirk asks Spock how he could have survived the encounter , McCoy jokes that his green blood must have left a bad taste in the creature ' s mouth , to which Spock informs the doctor that the sarcastic nature of his comments did not make them any less accurate . Due to his copper - based blood , he was not affected by the creature . Kirk enters the cabin and is about to report a strange sensation to Spock , when he is interrupted by Scott , who reports that the creature is moving out of the ship the way it came . Soon after , Kirk meets with Garrovick , recalling that he had been on the bridge during the attack . The ensign apologizes for violating orders , but , after commending his dedication , Kirk instead reminds him that , having been at the captain ' s side , he would have seen first - hand that phasers were ineffectual against the creature – since his hesitation made , even in Kirk ' s words , " no difference , " he could report for duty . Sensors indicate the cloud is moving off at high warp speed . Kirk , however , believes the creature had in Garrovick ' s cabin communicated its intent to go home . Course is therefore set for the planet Tycho IV , where the " Farragut " had encountered the creature eleven years earlier . McCoy logs his objections to the trip , as the medical supplies being brought by the " Yorktown " were urgent – and perishable . However , Kirk overrules him , particularly in light of Spock ' s conclusion that the evidence indicated the creature is going home to reproduce by fission – and by the thousands , it must be stopped as soon as possible . The officers agree to use antimatter to destroy the creature , in spite of the fact that a matter / antimatter blast would rip away half the planet ' s atmosphere and that transporters might not function in such an environment . They further agree to use hemoplasm to attract the creature . Spock volunteers to go down to the planet ' s surface since he was resistant to the creature ' corpuscle - draining attacks . However , Kirk overrules him and instead transports down with Ensign Garrovick . Kirk and Garrovick beam down to the surface of the planet with the hemoplasm and one ounce of antimatter , which has the explosive force of more than ten thousand cobalt bomb s . Unfortunately , while the antimatter is being primed , the creature takes the hemoplasm . As a result , Captain Kirk decides that he would use himself as bait . He orders Garrovick to return to the ship ; at this point , Garrovick attempts to overpower Kirk and force him to return to the ship , but is unable to do so . Both men remain on the planet and attract the creature , detonating the bomb just as it approaches them . On the " Enterprise " , Spock has some difficulty transporting them aboard . First , the crew tries to reset the transporter , then they cross - circuit to " A . " They then decide to cross - circuit to " B " , which enables them to beam the landing party aboard . Once safely aboard , Garrovick joins Kirk to hear some tall tales of his father ' s adventures . Memorable quotes . " " I need your advice . " " " " Then I need a drink . " " " " Monsters come in many forms . You know the greatest monster of them all , Jim ? Guilt . " " " " Intuition , however illogical , Mister Spock , is recognized as a command prerogative . " " " " You know , self - pity ' s a terrible first course . Why don ' t you try the soup instead ? " " " " A survey on Cygnian respiratory diseases ? I thought you took Garrovick some food . What were you doing with this ? " " " " Applying psychology . " " " " He saved my life , captain ; " I " should be lying dead in there , not him . " " " " Fortunately , " neither " of us is dead , ensign . " " " " Mister Spock , please don ' t take this the wrong way , but . . . why aren ' t you dead ? ! " " " " It ' s that green blood of his . " " " " My hemoglobin is based on copper , not iron " . " " " I ' ll bet he left a bad taste in the creature ' s mouth , too " " " " Colloquially expressed . But essentially correct . " " " " The way that thing can move , captain . I wouldn ' t believe it . " " " " Crazy way to travel ! Spreading a man ' s molecules all over the universe ! " " " " Captain , thank heaven ! " " " " Mister Scott , there was no deity involved . It was my cross - circuiting to B that recovered them . " " " " Well , then , thank pitchforks and pointed ears ! " " Background information . Remastered information . " Obsession " was the sixty - fifth episode of the remastered version of " The Original Series " to air , premiering in syndication on the weekend of . Aside from the standard CGI replacement footage of the " Enterprise " , this episode most notably featured new effects shots of the planets Argus X and Tycho IV , as well as revised footage of the dikironium cloud creature and the " Enterprise " s phaser fire into it while in space . One piece of new footage was added to this episode , a shot of the crater left from the antimatter blast on Tycho IV , shown at the end of the episode . This replaced stock footage of the " Enterprise " traveling through space . Links and references . References . 2257 ; AID cleanup ; analyst ; angle ; antigrav ; antimatter ; antimatter container ; Argus X ; autopsy ; bait ; blood ; blood count ; blood transfusion ; " Bones " ; bowl ; briefing room ; cc ; cobalt bomb ; command grade ; confined to quarters ; copper ; cordrazine ; crater ; deflector s ; deity ; detonator ; diamond ; dikironium ; dikironium cloud creature ; duty officer ; energy ; ; " Farragut " causalities ; " Farragut " s executive officer ; Federation survey vessel ; fission ; ; gold ; gravitational field ; growing season ; heaven ; hemisphere ; hemoglobin ; hemoplasm ; hereditary trait ; honey ; impulse engine ; incision ; intravenous ; iron ; ivory ; lead ; logic ; magnetic vacuum field ; matter ; medical log ; medical record library ; medical stores ; Milky Way Galaxy ; molecule ; molecular shift ; monster ; obsession ; on report ; ounce ; perimeter ; phaser station ; phaser - two ; pitchfork ; planetary survey ; plastic ; pollen ; price tag ; psychology ; pulse ; radioactive disposal vent ; radioactive waste ; record tape / tape record ; red alert ; red corpuscle ; respiration rate ; scanner ; senior officer ; shock wave ; soup ; spawn ; Starfleet Academy ; Starfleet survey vessel ; " Survey on Cygnian Respiratory Diseases , A " ; tall story ; Theta VII ; Theta VII colony ; time sync ; tricorder ; tritanium ; Tycho IV ; Tycho system ; ; ventilating system ; wood ; yard ; " Yorktown " , USS ; " Yorktown " s ship surgeon