Genesis ( episode ) " Enterprise " crew members de - evolve into prehistoric creatures after a medical treatment by Dr . Crusher goes wrong . Summary . Teaser . In sickbay , Nurse Alyssa Ogawa removes spines from Commander Riker ' s back ; an accident in the arboretum had resulted in a close encounter with a Cypirion cactus . Meanwhile , Lieutenant Barclay , having diagnosed himself with a lethal illness , goes to see Doctor Crusher – who assures him that he in fact is not suffering from any lethal illness at all , but instead has a mild case of Urodelan flu . Human s typically exhibit a natural immunity to the flu , but since the T - cell s that would normally fight off the infection are dormant , she activates that particular gene with a synthetic T - cell to let his body fight the infection naturally . Data soon arrives carrying his cat , Spot . The cat is here for a routine check on the progress of her pregnancy ; she is expected to deliver before the end of the week . The talk of babies prompts Ogawa to reveal that she is herself pregnant with her husband ' s child , prompting congratulations from Crusher . Act One . On the bridge , Lieutenant Worf ' s new weapons guidance system is being put to the test . However , out of three torpedoes launched , only two hit their targets , while the third swerves off course . With the unable to follow and disable the other torpedo due to a dense asteroid field ahead , Captain Picard and Data leave the ship to disarm the torpedo via a shuttlecraft . Before they leave , however , Data asks Barclay to watch over Spot . The cat might deliver before his return , and Barclay is one of the few people that Spot tolerates . As time passes on the " Enterprise " , several crewmembers start displaying strange behavior . After being ordered to take a break from checking the problems with the guidance system , Worf shows signs of becoming increasingly irritable and very hungry . Meanwhile , Counselor Troi finds the atmosphere too dry and cold , constantly changing around the ambient temperature and humidity levels and consuming large amounts of salt y foods and water . That night , Worf ' s behavior degenerates further and becomes more primal : he rips up his bed and sleeps tensely on the floor . Act Two . In engineering , Lieutenant Barclay shows his own strange behavior . He seems unusually energetic , speaking so rapidly that La Forge and Riker are having difficulty keeping up with him . Riker ' s inability to keep up with Barclay is compounded by his own problems ; he is having trouble with his memory and higher thinking . On the bridge , Troi ( currently on watch ) keeps trying to raise the temperature , and Worf keeps turning it back down : complaining it is too hot . Troi finally leaves the bridge to take a bath in her quarters . A problem detected in engineering has Barclay and La Forge in the Jefferies tube s . Barclay finds and bypasses a ruptured plasma conduit . As he does , La Forge detects cholic acid around the hole in the bulkhead where the ruptured line was located . The bulkhead and conduit seems to have been dissolved by an organic solvent . But in contrast to Barclay ' s increasing hyperactivity , La Forge seems increasingly lethargic . Barclay suggests a biospectral analysis ; La Forge agrees before deciding to take a break . The changes being experienced by the crew continue to progress . Riker finds himself unable to either remember the recent weapons testing or respond to a Starfleet request for a report on the matter . Troi sits in her bath tub , wearing her Starfleet uniform , trying to stay wet when Worf suddenly enters her quarters , approaches Troi , and bites her cheek . Both Troi and Worf are taken to sickbay , and Crusher quickly notices the changes . When Ogawa adds that more of the crew are experiencing symptoms , but while some are also finding the temperature too cold there are others who have developed fever s , leading Crusher to conclude that something is spreading around the ship . She then turns her attention to Worf who is completely unresponsive , and notices something else : he has swellings under his jaw that appear to be venom sacs . They prove to be just that as Worf suddenly sprays venom in Crusher ' s face , then flees sickbay before he can be captured . In the observation lounge , Ogawa reports that she got Crusher into stasis before she became paralyzed by the venom . She will require reconstructive surgery , but Ogawa believes she will be all right . However , there is still the problem of the mysterious illness affecting the crew . Barclay reports that the venom that affected Crusher has been found in other parts of the ship , including at the ruptured plasma conduit seen earlier . Riker admits to his inability to think straight ; he can ' t think properly when La Forge ( now serving as acting first officer ) reports on having trouble locating Worf on sensor s . He dismisses the senior staff and tries to send a subspace message to Starfleet concerning their problem , but finds himself unable to recall the codes required . Act Three . Picard and Data are a little puzzled to not be able to locate the " Enterprise " . A quick search locates the ship , visibly adrift . Upon docking , they ascertain that the ship ' s power systems are down , environmental systems are configured strangely , and where there should be over a thousand humanoid lifeforms there seems to be a near - equal number of myriad creatures . Some of the characteristics are inconsistent with those of the known crew , such as casting off skin like a reptile . They come upon Troi ' s quarters and discover her in her bath tub , having somehow developed into an amphibian - like creature . It is their first clue that the crew is undergoing unusual changes . Seeking to stabilize the ship , they then go to the bridge , finding it in shambles , with a dead Ensign at the conn ( from what appears to be an animal attack ) , his spine fractured in three places ; he had also been affected , but was killed before undergoing any significant changes . From the bridge , Data is able to note that the crew is still on board the ship but in a similar state to that of Troi . Many of them have been gravitating towards water ( the aquatic lab ) and plants ( the arboretum ) . Picard is unable to restore power to the ship due to the entire power - transfer grid being damaged . Suddenly , they hear a noise coming from the ready room . There they discover Riker , now a brutish proto - Human , attacking the captain ' s aquarium ( in which Livingston , the captain ' s lionfish , has also devolved into a jellyfish ) . When he charges them , Data stuns Riker with his phaser . Based on what they ' ve encountered so far , Data announces his hypothesis that the crew is de - evolving . Act Four . Troi and Riker are taken to sickbay for further analysis . Data , after analyzing Riker ' s DNA , discovers that a synthetic T - cell has invaded his genetic code s and has begun to activate his latent intron s , a result of Crusher ' s treatment of Barclay . He explains that introns are genetic codes which are normally dormant ; they are sequences of DNA which provided key physical and behavioral characteristics millions of years ago , but are no longer necessary . Counselor Troi ' s gill - slits and other amphibious characteristics , for example , are derived from introns which contain amphibious codes . Because introns can include genetic material from many different species over millions of years of evolution , it is possible that a wide variety of transformations is occurring among the crew . Since all humanoid life has a similar genetic pattern , the virus will work similarly on all non - Human lifeforms as well , and they will each be de - evolving to earlier forms of life in their homeworlds . He informs Picard that he has also been infected by the intron virus , and is now slowly de - evolving into an earlier form of primate . Realizing that they do not have much time , they decide to act quickly . Since Data ' s computer in his quarters operates independently from the ship ' s computer and is probably still intact , they decide to go there in order to examine the situation further . Arriving at his quarters , Data notices that Spot , who has been expecting a litter of kitten s , has finally given birth . A further search finds a reptile wearing her collar ; they soon realize that the reptile is Spot and that the intron virus is capable of also affecting non - humanoids . Her kittens , however , do not seem to have been affected by the virus that has been plaguing the rest of the crew . Given that Spot ' s kittens are unaffected , Data and Picard conclude that the placental barrier s and amniotic fluid that serve as a filtration system to protect the fetus in the placenta have probably prevented the intron virus from being passed on from Spot to her kittens . They decide that they probably can inhibit the intron virus by using the natural antibodies in Spot ' s amniotic fluid . However , in order for it to be effective on humanoid crewmembers , humanoid antibodies would be necessary . Recalling that Nurse Ogawa is expecting , they track her down to the arboretum . But before they can begin tracking her down , a failure in a warp plasma vent forces them to detour to main engineering so Data can program repairs . While checking on the warp core , Picard is frightened by the sudden appearance of Barclay , partially transformed into a spider . Data surmises that his terror at the sight ( a result of the heightened sense of awareness found in small primates ) is an initial symptom of Picard ' s de - evolution ; they need to hurry . They locate Ogawa ( who is apparently partially de - evolved into a proto - Human ) and Data begins to analyze Ogawa ' s fetus , confirming that it is not affected by the virus . He says that he can use her amniotic fluid as a template for a retrovirus which in turn would neutralize the synthetic T - cell and re - establish the genetic patterns of each host . While working on finding a way to most quickly address the situation , something pounds on the sickbay door . Life sign scans show something big , armored , and Klingon ; it is Worf . Act Five . A transformed Worf tries to force his way into sickbay . He appears to be seeking something or someone particular . Picard notices that the bite Worf gave Troi was not to hurt her but rather seemed part of a mating process , and that it appears as if Worf had come back for her . The situation becomes increasingly dangerous as an ever angrier and aggressive Worf almost breaks through the door . Data and Picard cannot just abandon Troi and the others in sickbay , but at the same time , Data needs to continue with his analysis of the amniotic fluid . Picard , who is beginning to experience the effects of the virus himself , suggests distracting Worf and luring him away from sickbay . He suggests extracting pheromone s from Troi ' s sebaceous glands to lure Worf away from sickbay so Data can continue his work and the others are safe . While Data continues work on the retrovirus , Picard leads Worf on a chase through the " Enterprise " s corridor s until becoming cornered at the ruptured warp plasma conduit La Forge and Barclay had been repairing earlier . Picard improvises , sitting upon the insulated access panel and using the bypassed conduit to send electricity through the Jefferies tube , knocking out Worf . At that moment , Data reports that he has completed the retrovirus . It will make the introns in the crew dormant again ; at Picard ' s consent , he floods the ship with a gas eous form of the new virus , turning the crew back to normal . In sickbay , Barclay nervously asks Dr . Crusher if all this was his fault . She states that actually it was " her " fault for having activated a dormant T - cell which , in turn , activated " all " dormant T - cells ( including the introns ) . She suggests naming the virus after Barclay , calling it the Barclay ' s Protomorphosis Syndrome . Jokingly , she tells Troi that Barclay not only devolved into a spider , but also had a new disease named after him . Troi sighs , realizing that she better clear her calendar for the next few weeks . Memorable quotes . " " Reg , you don ' t have Terellian Death Syndrome ! " " " " Are you . . . you ' re sure ? " " " " I ' m sure . " " " " I have spent the past nine weeks as an expectant parent . I would be happy to share my insights with your husband . If my experience is any indication , he will need all the help he can get . " " " " The torpedo is out of range . " " " " Even for your newly improved phasers ? " " " " Mr . Worf . . . I think that you should consider analyzing your new guidance system . " " " " Doctor ! My capillaries are shrinking ! " " " " She ' s such a sweet little kitty . " " " " She is to you . " " " " Do not approach me unannounced – especially while I am eating . " " " " Worf . . . open your mouth . " " " " Are you saying that Worf is spraying this . . . " " " " VENOM ! " " " " . . . this venom . . . all over the ship ? " " " " I ' d say so ! " " " " Well . . . before I begin swinging through the ship , looking for breakfast , we need to find some answers . " " " " What – what ' s that ? " " " " It is large , approximately two hundred kilograms . It is heavily armored with an exoskeleton . Life signs appear to be . . . Klingon . " " " " Worf ! " " " " Do you think he sees us as prey ? " " " " There are crewmembers in the corridors and other sections of the ship . It would be easier for him to capture and consume one of them than attempt to break through a door . " " " " Well , Mr . Worf . . . let ' s hope when you wake up you ' re a new man . " " " " He transformed into a spider . . . and now he ' s had a disease named after him . " " " " I think I ' d better clear my calendar for the next few weeks . " " Links and references . References . amniotic fluid ; amniotic scan ; amphibian ; appetite ; aquatics lab ; arachnid ; arboretum ; artery ; australopithecine ; Barclay ' s Protomorphosis Syndrome ; bath tub ; Betazoid ; biobed ; biology ; bioscan ; biospectral scan ; burp ; capillary ; cats ; caviar ; centigrade ; cholic acid ; collar ; corrosion ; Cypirion cactus ; dizziness ; DNA ; Earth ; electrophoretic activity ; epidermal layer ; fever ; filtration system ; Hacopian ; ; hominid ; " Hypatia " ; hyper - evolution ; hypochondria ; hypothalamic series ; iguana ; immunity ; intravascular pressure ; intron ; Jefferies tube ; K - 3 cell ; K - 3 cell count ; Klingon ; lemur ; litter ; Livingston ; medical tricorder ; microcellular scan ; molt ; mutation ; nictitating membrane ; Number one ; Ongilin caviar ; palpitation s ; pheromone s ; photon torpedo ; placental barrier ; ; pygmy marmoset ; reconstructive surgery ; retrovirus ; ribocyatic flux ; saliva ; sebaceous gland ; Selar ; shivering ; shock ; sickbay ; ; solvent ; Spot ' s kittens ; spread pattern ; Starfleet Medical Database ; stasis ; Symbalene blood burn ; T - cell ; Terellian Death Syndrome ; Type 6 shuttlecraft ; Urodelan flu