text: one of us ( lost ) " one of us " is the 16th episode of the third season of lost . it aired on april 11 , 2007 , making it the 65th episode of the series . the episode was written by carlton cuse and drew goddard and directed by jack bender . the title of the episode is not only a reference to the season two episode titled " one of them " , it is also a major theme of the episode , as jack tries to convince the other flight survivors that juliet is " one of us " , rather than an other . the character of dr. juliet burke ( elizabeth mitchell ) is featured in the episode 's flashbacks , which reveal how juliet got on the island and why she went to the island in the first place . while on the island , jack shephard ( matthew fox ) , kate austen ( evangeline lilly ) , sayid jarrah ( naveen andrews ) and juliet trek back to the beach camp , and claire littleton ( emilie de ravin ) is struck by a mysterious illness . andrew divoff , william mapother and nestor carbonell again reprise their recurring roles as others ; mikhail bakunin , ethan rom and richard alpert . the island events in this episode take place between december 13 and december 15 , 2004 . plot flashbacks juliet arrives at an airport with her sister , where richard alpert and ethan rom are there to escort her the rest of the way . juliet says good - bye to her sister , rachel , promising to be back before her baby is born . in the airport terminal , alpert pours sedative into a glass of orange juice and gives it to juliet to drink , explaining that the trip is very intense . juliet is wary of drinking the juice , even though she is okay with the other circumstances surrounding the trip . alpert interrupts and tells her the place she is going is very special and that she has a gift with which she is supposed to do something significant . juliet drinks the orange juice and passes out . she wakes up in a submarine with her arms and waist strapped down for safety . she then moves out onto a dock , where she meets ben linus . juliet is shown operating with ethan and goodwin ( brett cullen ) on a pregnant patient , sabine , who dies ; she is comforted by goodwin . juliet meets with ben , and explains her theory that the problems with pregnant women happen at conception . she wants to test this theory by having a woman conceive off the island , but ben refuses to let anyone off the island . when juliet tells him that nothing else can be done and asks to go home and be with her sister , ben informs juliet that her sister 's cancer has come back . he offers her a choice : either juliet can go home and be with her sister as she dies , or she can stay and he will have jacob cure her sister 's cancer . juliet is in bed after sleeping with goodwin . afterwards , she is given x - rays of ben 's back , and when she determines that ben has a tumor , she confronts him and accuses him of lying about rachel . he denies lying to her and refuses to let her go home . the next day , immediately after flight 815 crashes , ben takes juliet to the flame station to see mikhail . ben tells mikhail that he wants information on all of the passengers of the plane , then asks him to bring up a live feed . on the screen a newspaper is shown with the current date , september 22 , 2004 , followed by a shot of rachel playing with her child ( rachel named her son julian , presumably after juliet ) in a playground , and ben explains that her cancer is in complete remission . the final flashback shows juliet and ben discussing their plans immediately before the events of " left behind " . ben tells her to handcuff herself to kate and say she was left behind . she is also told that claire 's " implant " has been " activated " and that this will make claire ill . juliet is to use drugs left at the drop point to cure her and earn the trust of the survivors ; ben gives her a gas mask and leaves . while setting up her shelter , juliet looks around the camp and ties a final double knot as jack smiles at her . on the island jack shephard , kate austen , sayid jarrah and juliet burke move back to the beach camp . as they stop for the night , jack explains to kate the deal he made with ben linus ( michael emerson ) . sayid attempts to interrogate juliet , but jack intervenes and defends her . at the beach camp , charlie pace ( dominic monaghan ) hears claire littleton 's baby , aaron , crying and wakes up claire . claire says she is not feeling well , so charlie offers to take care of aaron . james " sawyer " ford ( josh holloway ) sees jack , kate , and sayid returning . though happy about their return , he expresses his displeasure at seeing juliet . hugo " hurley " reyes ( jorge garcia ) engages juliet in casual conversation . juliet guesses that hurley was sent to keep an eye on her . he tells her the last other who came over , ethan , was killed and buried nearby . that night , jack tells everyone that he trusts juliet and that should be enough , but sayid disagrees . jack continues to explain that john locke blew up the submarine that was to take him home . claire suddenly collapses with blood gushing from her face . juliet takes jack and kate aside and tells them she knows what 's wrong with claire because she did it to her . at the camp , juliet explains that claire 's immune system has turned against her due to a latent reaction to medication in her bloodstream . the medication was designed by juliet to keep claire alive during her pregnancy . she was brought to the island to find out why women couldn 't have children . the mother 's body treats the pregnancy as a foreign invader and the immune system attacks ; every pregnant woman on the island has died . claire was the first to survive even though she showed some of the symptoms . juliet explains that ethan kept a stash of the serum at a nearby drop point . she goes out into the jungle and retrieves the serum , but sayid and sawyer have followed her , and they want answers . juliet tells them there is no time , and realizing they are not going to budge , she stands up to them and says she finds it interesting that they are the camp 's moral police , considering their violent pasts . she takes the serum back to the beach and gives it to jack . he warns her that if anything happens to claire , he will not be able to protect her against the will of the survivors any longer and she would be alone , to which juliet states that she already is . at the camp , claire wakes up . she is feeling and looking much better . juliet is now on the path to being trusted by the survivors . jack brings her supplies to set up her tent area and tells her eventually everyone will need answers . juliet asks why jack trusts her and does not ask for answers . he says because when the submarine exploded , he saw in her eyes that she wanted to get off this island more than anything . that makes her " one of us . " production " one of us " was the nineteenth episode directed by jack bender . it was written by carlton cuse and drew goddard ; the pair had never before collaborated on an episode . as usual , the scenes on the beach ( the survivors camp ) were shot at oahu 's papa beach , while the island scenes were actually filmed at the waialua ranches . the secure building exterior scenes were shot at the honolulu advertiser production and distribution building . most of the scenes displaying the others ' camp were shot at the hawaii film studio , with the exception of the barracks which were filmed at ymca camp erdman . the inside of the submarine was filmed inside the ss - 287 which is located at the uss arizona memorial . once again , the song " downtown " by petula clark was used in flashbacks ; it was already used in the earlier episode " a tale of two cities " . reception " one of us " was watched by 12 . 09 million americans , ranking lost as the twentieth most watched program of the week . lost defeated cbs ' csi : ny by 53 % among adults 18 - 49 , the largest ever margin of victory for lost over csi : ny in original episodes . the ratings were also an increase over the previous episode , and improved the timeslot by 5 . 7 million viewers over the same night last year . lost was the fifth most watched program for the week in the key adults 18 - 49 demographic , achieving 5 . 2 million viewers . in the united kingdom , the episode attracted 1 . 09 million viewers , and was the second most watched program of the week on the non - terrestrial channels , beaten only by live fa cup football . reviewer chris carabott of ign rated the episode with an 8 . 7 out of 10 , commenting that " one of us " was " yet another solid effort from long - time lost director jack bender who deserves credit for bringing us some of the best episodes the series has to offer . bender has helmed " walkabout " , " man of science , man of faith " and this season 's best " the man from tallahassee " just to name a few " . buddytv senior writer jon lachonis commented that " one of us " was " perhaps the most perfect episode of lost ever produced , bar none . for those of you who were upset with how inelegantly " exposé " squandered its flashback opportunities , prepare for a huge apology from the producers . for those lost fans who stuck around knowing that the show would obtain that mythical level of greatness that seemed to come so natural , here is your pay - off . " in this same review , he complimented elizabeth mitchell on her portrayal of juliet . mitchell submitted this episode for consideration for outstanding supporting actress in a drama series at the 59th primetime emmy awards .