Extinction ( episode ) Archer , Reed , and Sato are threatened by a virus that mutates them into a primal lifeform . Summary . Teaser . In a jungle , space - suited aliens are chasing down a primal - like creature whom they promptly kill with their flame thrower s . Act One . On the , it is late at night . Commander visits Sub - commander T ' Pol for a long - overdue massage session . To make up for missing the past two sessions , he brings some Georgia peach es which he got from Earth recently . T ' Pol uses Vulcan techniques , but assures Tucker the risk of paralysis is minimal . The session is cut short as Captain Archer calls T ' Pol away . He is able to discover , from the Xindi ' s stolen database , the last planet ary stop of the destroyed Xindi ship . These new Xindi seem to be evolved from primate s . T ' Pol notes they aren ' t necessarily the ones that attacked Earth , but Archer wants more information , ordering a course . Upon arrival at the planet , " Enterprise " doesn ' t detect life sign s , but does discover a metal lic signature on the planet . Leaving Travis Mayweather in command , Archer leads an away team of Lieutenant Malcolm Reed , Hoshi Sato , and T ' Pol , and eventually discovers a Xindi landing craft and some scorched corpses – not Xindi . However , soon the away team is affected by a virus as they explore the surrounding area . T ' Pol feels her temples bulge , and , upon seeing Reed again , she sees he has transformed into a primal - like creature . She heads back immediately to the landing craft , only to discover that Archer is now also infected . T ' Pol immediately calls for a security team from " Enterprise , " but is soon attacked by Archer , now speaking in an alien language . She stuns him in a defensive maneuver , only to be attacked by Sato from her side , also transformed . T ' Pol attempts to run away but falls and is rendered unconscious . Act Two . The troop of new mutants carries T ' Pol ' s body using sticks and branches to a clearing and lays her down . As she wakes , the three seem to be having a discussion about her . T ' Pol is tied up and , in a highly agitated state for a Vulcan , asks them to untie her . Archer does so , but seemingly under protest from Sato . Then , T ' Pol convinces them to give her the universal translator and tries to get them to talk . On the " Enterprise " , Doctor Phlox examines the new bio signs and is confident he sees a Vulcan one . The other three are not . Tucker wonders where their team is . Tucker wants to go down after them , but Phlox warns him , saying that T ' Pol mentioned being " altered , " and is guessing she meant literally . He wants more time to investigate , but Mayweather sees they ' re moving off , and Tucker decides he can ' t wait any longer . He orders the other prepared and environmental suit s . T ' Pol makes some progress talking to them and trying to convince them to get back to the ship . However , she discovers they have a purpose : they are looking for Urquat . Sato and Reed are insistent on finding the rest of " their people , " and that T ' Pol is laying to them . Archer hesitates . They obviously are intent on finding this Urquat , so T ' Pol then tries allowing them . On the way , she sees more of their primal behavior , as Reed climbs a tree incredibly fast and finds food , which is immediately fought over by the three . Archer having wrestles some food from Reed . Before he eats , he interestingly tries to offer T ' Pol some of it , but she refuses . He then also allows Reed to have some . Tucker takes down a rescue team of Corporal Chang and Private Palmer and they start searching . The mutants , with enhanced vision , have an advantage in observing the team from the foliage . Soon , Reed attacks Chang and knocks him out as Sato runs by Palmer , drawing him away . Tucker catches up with Chang , stuns Reed as he attacks again , then is attacked at close range by Archer . Archer bashes a crack in Tucker ' s helmet and intends to go again but T ' Pol stops him , asking if he recognizes Tucker . Archer pauses to consider , but Palmer gets close and he runs away . T ' Pol decides to stay with Archer and Sato , ordering Tucker to take Reed back to the ship . A primal Reed is highly agitated in the decon chamber while Phlox observes him . Phlox confirms to Tucker they have a mutagenic virus and that T ' Pol ' s Vulcan K - cell s are apparently neutralizing the virus . He needs her active DNA as soon as possible to complete the cure . However , two alien ships intercept " Enterprise " and declare them under quarantine . He demands they prepare to be boarded . Act Three . Tucker refuses to allow anyone on " Enterprise " , but the alien commander , Tret , says he detects the infected crewmember and that the virus must be eradicated , having been studied for 60 years without another option . Tucker is emphatic that there is no " outbreak " as Reed is in medical isolation . He invites the commander to the ship to discuss it , but promises a fight if he tries to board by force . On the planet , Archer has a dream in which he discovers the great city of Urquat underground . Oddly , he sees himself ( as a Human ) approach him , jolting him awake . He happily tells Sato about the city , and they ' re both excited . T ' Pol tries to state that his home is really Earth , but they both declare she ' s lying . Tret comes aboard " Enterprise " and visits sickbay to observe Reed and inform Phlox and Tucker about the virus . He warns them that the virus is very dangerous and millions of his people had to be killed because of its rapid growth . An ancient race , called the Loque ' eque , created the virus to perpetuate their race as they could no longer propagate . Tret ' s people intend to eliminate all infected victims as the virus spreads like wildfire and drives all who change into Loque ' eque to find their home . Tret gets word from his ship that more infected are on the planet , and he orders a containment team together . Phlox says T ' Pol is immune , and wants to work together with Tret , but Tret is insistent on examining them himself . He leaves , promising use of force if he is hindered from containing the outbreak . After , Phlox says he needs T ' Pol ' s DNA within two hours , and Tucker gets an idea , remembering she bit into one of the peaches . On the planet , the three close in on the city , however , they discover the lifeless ruins of Urquat . Act Four . Archer and Sato can ' t believe the city is gone , and dwell on it . T ' Pol tries to say they can go to " Enterprise " to find out what happened to them , but Archer refuses . Then , he suggests it was T ' Pol ' s race that destroyed them , and holds her by the neck as she denies it . Then , they are discovered by the aliens searching to destroy them , so they run . The three of them attack the aliens in caves and , in the ensuing melee , they are knocked out and the three escape to the surface at T ' Pol ' s insistence . However , Archer manages to tear the suit of one of the aliens , thereby infecting him . His comrades promptly " torch " him when they find him . The three make it outside of the caves but are soon surrounded by the aliens . They force T ' Pol away and prepare to torch the other two , but just then Tucker and the MACO s appear and stun the aliens . T ' Pol makes a final plea to Archer to follow her to the shuttlepod , and he finally agrees . As they approach the ship , Tucker orders Mayweather out of orbit , and they are soon chased by the alien containment force . Tucker tries to buy time for Phlox , but after being fired upon briefly , Tret hails them and orders them out of warp . Tucker pleads with him to allow them to find a cure . Tret dismisses it until he see the partially - cured Sato and Archer appear on the bridge . Tret has the ship scanned again and the aliens finally accept that a cure is possible , and break off the attack . Dr . Phlox wants to destroy the last of the mutagenic virus , thereby possibly eliminating the last vestiges of the Loque ' eque . Archer doesn ' t want that to happen and orders the doctor to put the vial in stasis . Archer assumes that the unnamed aliens will destroy the last traces of the virus on the planet with their new cure . He reasons that soon the last trace of this civilization will be Dr . Phlox ' s sample . Memorable quotes . " " You sure this is safe ? I mean , has anyone ever tried it on a Human before ? " " " " Not to my knowledge . The risk of paralysis is minimal . " " " " You ' re saying these alien bio - signs could be our people ? " " " " From what we ' ve seen of the Expanse , it ' s a possibility we have to consider . The laws of biochemistry on this world may be just as unpredictable as the laws of physics . " " " " He didn ' t even recognize me . " " " " Don ' t be offended . In his current condition , I doubt he ' d recognize any of us . " " " " Your ship is in restricted space . " " " " Sorry . It wasn ' t very well marked . " " " " Your vessel is under quarantine . Prepare to be boarded . " " " " Have you got anything for my stomach ? Chef ' s food isn ' t sitting too well . " " " " Until your digestive tract is fully restored , you may want to avoid the mess hall . " " " " What do you suggest I eat ? " " " " You ' re welcome to some of the moth larvae I feed to my Pyrithian bat . " " Links and references . References . 2090s ; antivirus ; biochemistry ; bio - hazard protocol ; blood ; ; chromophyllic plant species ; command center ; Delphic Expanse ; digestive tract ; DNA ; Earth ; ecosystem ; equatorial islands ; EV suit ; digestive tract ; Georgia ; humanoid ; immunity ; K - cell ; larva ; Loque ' eque ; Loque ' eque homeworld ; Loque ' eque language ; moth ; mutagenic virus ; neural node ; oxidation ; peach ; Pyrithian bat ; quarantine ; serum ; " " ; " Shuttlepod 2 " ; ; transporter ; Tret ' s containment vessel ; Tret ' s species ; Urquat ; Urquat citizens ; Vulcan ; Xindi - Arboreal ; Xindi - Arboreal landing craft ; Xindi database