No . overall No. in season Title Directed by Written by Original air date Prod . code U.S. viewers ( millions ) 23 `` The Return '' J. Miller Tobin Kevin Williamson & Julie Plec September 9 , 2010 ( 2010 - 09 - 09 ) 2J5251 3.28 Picking up where the first season left off , Elena arrives home to discover the fates of Uncle John and Jeremy . Jeremy has not transitioned into a vampire , because he did not take enough drugs to die and Anna 's blood overcame the overdose . Damon , Bonnie , and Elena agree that Caroline needs Damon 's blood to survive . Damon realizes that Katherine has returned and is impersonating Elena. Tyler is surprised when his uncle , Mason Lockwood , arrives in town to console him . Katherine and Damon nearly sleep together , but Katherine tells Damon , `` it will always be Stefan '' . Distraught , Damon goes to see Elena , who resists his attempt to kiss her . Angry that Elena also loves Stefan , Damon snaps Jeremy 's neck . Jeremy survives because he is wearing a Gilbert ring , which protects the wearer from death from supernatural causes . Katherine goes to the hospital and smothers Caroline with a pillow . Before Caroline dies , Katherine gives her a message for the Salvatore brothers : `` Game on . '' 24 `` Brave New World '' John Dahl Brian Young September 16 , 2010 ( 2010 - 09 - 16 ) 2J5252 3.05 Caroline has become a vampire and awakens in the hospital craving blood . Tyler catches Mason searching for a moonstone , which is a family heirloom . At the carnival , Damon compels a boy named Carter to pick a fight with Tyler to provoke one of Tyler 's bursts of anger . Mason breaks up the fight using his supernatural abilities , proving that he is a werewolf . Caroline confronts Damon about his abusive treatment , and he realizes that she is a vampire . He alerts Elena and Stefan , while a ravenous Caroline drains Carter . Stefan promises Caroline he will guide her journey as a vampire. Tyler retrieves the moonstone Mason has been seeking . Matt notices Caroline 's erratic behavior but admits that he loves her . 25 `` Bad Moon Rising '' Patrick Norris Andrew Chambliss September 23 , 2010 ( 2010 - 09 - 23 ) 2J5253 3.57 Elena , Damon , and Alaric head to Isobel 's old office at Duke University , where it is revealed that vampires and werewolves used to roam freely until a shaman uttered a curse to limit their powers , after which the werewolves were servants of the moon and vampires became the slaves of the sun . Stefan teaches Caroline how to control herself and hunt animals . Bonnie makes Caroline a daylight ring so that she will not be burned by the sun . In werewolf form , Mason encounters Stefan and Caroline. Tyler saves them by shouting at the werewolf ; he later finds Mason in the woods and realises what has happened . Unable to control herself , Caroline feeds on Matt . She compels him to forget it , but ends their relationship to keep him safe from her . Damon tells Elena Katherine 's real name , Katerina Petrova , to aid Elena with her research . Alaric reaffirms his romantic interest in Jenna , and Caroline finds Katherine in her bedroom . 26 `` Memory Lane '' Rob Hardy Caroline Dries September 30 , 2010 ( 2010 - 09 - 30 ) 2J5254 3.18 Katherine tells Stefan that she will kill Elena unless he ends his relationship with her , and as a result , Elena realizes that Caroline is working for Katherine . Elena and Katherine finally meet , but Katherine ignores Elena 's questions . Damon stabs Mason with a silver knife , but Mason says it is only a myth that silver hurts werewolves . They are now enemies . Katherine remembers how in 1864 , after Stefan and Damon were shot in an attempt to save her , she had kissed Stefan , declaring her love and saying they would be together again one day . Stefan and Elena stage a fake break - up to prevent Katherine from hurting anybody . 27 5 `` Kill or Be Killed '' Jeff Woolnough Mike Daniels October 7 , 2010 ( 2010 - 10 - 07 ) 2J5255 3.47 At the Mystic Falls picnic , Mason Lockwood tells Sheriff Liz Forbes that Stefan and Damon are vampires . Liz and her fellow police officers shoot Stefan and Damon . Caroline and Elena reach the Salvatore 's before Liz can kill them , but Caroline 's identity as a vampire is exposed to her mother . Liz rejects Caroline as her daughter , and Stefan drinks Elena 's blood to gain strength . Caroline confesses to Elena that Katherine had threatened to kill Matt if Caroline did n't spy on Elena and Stefan for her ; Elena forgives Caroline . Jeremy and Tyler start to bond when Tyler learns that Jeremy knows about the curse . Tyler almost kills a girl , feeling for a second that he wants her to die . He then tells Mason that he wants nothing to do with the curse , and gives him the moonstone . It is revealed that Mason is working for Katherine , who wants the moonstone , and that they are lovers . 28 6 `` Plan B '' John Behring Elizabeth Craft & Sarah Fain October 21 , 2010 ( 2010 - 10 - 21 ) 2J5256 3.62 Liz accepts Caroline , and Caroline compels her mother to forget that she is a vampire . Bonnie incapacitates Mason by giving him an aneurysm . Damon then questions and tortures Mason who , believing that Katherine loves him , refuses to talk . Telling Mason that Katherine is using him , Damon eventually kills him . Bonnie has a vision of the moonstone 's location in a well . Stefan discovers that the well is full of vervain , which burns him . Caroline and Bonnie help Elena rescue Stefan and retrieve the moonstone . Katherine compels Jenna to stab herself . Fearful of what else Katherine might do , Elena breaks up with Stefan for good . Needing another werewolf , Katherine compels Matt to attack Tyler , so that Tyler will kill Matt and become a werewolf . 29 7 `` Masquerade '' Charles Beeson Kevin Williamson & Julie Plec October 28 , 2010 ( 2010 - 10 - 28 ) 2J5257 3.55 Stefan , Damon , Bonnie , Jeremy , Alaric , and Caroline plan to kill Katherine at the Lockwoods ' masquerade ball . Katherine is visited by Lucy , a witch who is to help her retrieve the moonstone . Under Katherine 's compulsion , Matt fights Tyler . Caroline breaks up the fight , but Sarah , who is also compelled , stabs Tyler , and he accidentally breaks her neck . Tyler 's eyes turn yellow , showing that the curse has been triggered . Stefan and Damon try to kill Katherine , but they stop when Jeremy tells them that every time they stake her , Elena is wounded . Katherine reveals that she had Lucy put a spell on Elena and herself , which linked them . Lucy , who is Bonnie 's cousin , lifts the spell and incapacitates Katherine , who collapses . Damon traps Katherine in the underground tomb . As Elena heads home she is intercepted by a masked stranger . 30 8 `` Rose '' Liz Friedlander Brian Young November 4 , 2010 ( 2010 - 11 - 04 ) 2J5258 3.63 A vampire named Trevor takes Elena to an abandoned house , where she meets Rose , another vampire . When Tyler witnesses Caroline 's abilities , she reveals that she is a vampire . Elena overhears Rose and Trevor arguing about a vampire named Elijah . Using a spell , Bonnie locates Elena . Elena tries to extract information from Rose , who tells her that Elijah is one of the `` original '' vampires . Rose and Trevor are using Elena , the Petrova doppelgänger who is the key to breaking the curse , as a bargaining chip . Elijah arrives , and Rose offers him Elena in exchange for their pardon . Elijah agrees but kills Trevor . Elena tries to stall Elijah by saying that she knows where the moonstone is , but he compels her to tell him its location . Stefan and Damon arrive to fight with Elijah and stake him . Elena 's vervain necklace remains at the house . Later that night , Damon is in Elena 's bedroom with her vervain necklace in his hand . He tells her that he loves her but does n't deserve her , and that Stefan does . Then he compels her to forget what he said . In the abandoned house , Elijah pulls the wooden stake out of his chest . 31 9 `` Katerina '' J. Miller Tobin Andrew Chambliss November 11 , 2010 ( 2010 - 11 - 11 ) 2J5259 3.50 This episode 's plot summary may be too long or excessively detailed . Please help improve it by removing unnecessary details and making it more concise . ( November 2016 ) ( Learn how and when to remove this template message ) The episode begins in Bulgaria in 1490 and shows Katherine giving birth to a baby girl . Her father says that she has shamed their family and takes the baby away . In the present , Elena goes to the tomb , where she offers Katherine blood in exchange for the truth - that a doppelgänger from the Petrova line can be used to break the curse . As Katherine 's descendant , Elena is the current Petrova doppelgänger . Katherine reveals that she was expelled from Bulgaria and fled to England , where Elijah and Trevor found her . They recognized her as the Petrova doppelgänger and Elijah tried to kill her , but Trevor helped her to escape . She became a vampire so that she could not be used to break the curse . Katherine came to Mystic Falls to offer Klaus what he needed to lift the curse : the current doppelgänger , a witch , a werewolf , a vampire , and the moonstone . She hoped that Klaus would spare her life in exchange for this . Bonnie meets a warlock named Luka and his father . Jeremy is jealous of Bonnie 's attraction to Luka . Damon and Rose seek information about Klaus from Rose 's vampire friend , Slater , but a healed Elijah overhears them . Damon and Rose sleep together , and Elijah compels Slater to stake himself . It is revealed that Luka and his father are working for Elijah . 32 10 `` The Sacrifice '' Ralph Hemecker Caroline Dries December 2 , 2010 ( 2010 - 12 - 02 ) 2J5260 3.46 Elena and Rose go to ask Slater about Klaus , but they find his staked corpse . Elena uses information from Slater 's computer to get Klaus 's attention , saying she wants to surrender . Caroline and Tyler discover Mason 's journal and the video diary that he used to document his transformations . Bonnie plans to lift the spell from the tomb and incapacitate Katherine so that Stefan can grab the moonstone , but Jeremy goes ahead with the plan alone and is captured by Katherine , who feeds on him . Stefan saves Jeremy but is trapped himself . Three vampires confront Damon , Rose , and Elena . Elijah kills the three vampires and then departs . Back home , a trapped Stefan makes Damon promise to protect Elena . Elijah informs Luka 's father that Damon and Stefan will protect Elena , which is Elijah 's goal . 33 11 `` By the Light of the Moon '' Elizabeth Allen Mike Daniels December 9 , 2010 ( 2010 - 12 - 09 ) 2J5261 3.16 As the full moon approaches , Caroline helps Tyler prepare for his transformation . Stefan asks Katherine to prove that there is good in her , and she advises him to ask Isobel for help in finding Klaus . Bonnie seeks Luka 's help to destroy the moonstone ; they cast a spell , but Luka gives the moonstone to his father . Jules , a friend of Mason , arrives in Mystic Falls looking for him . Damon and Alaric try to trick her into having a drink mixed with wolfsbane . She reveals that she is a werewolf and tells Damon that he has been marked . Elijah makes a deal with Elena : she has to keep herself safe from Klaus ( so that Elijah can use her as bait to kill Klaus ) and in return , Elijah will protect her friends and family and free Stefan from the tomb . Caroline reunites with Tyler . At the Salvatore mansion , Jules , in wolf form , tries to attack Damon but instead bites Rose 's shoulder , which becomes infected . 34 12 `` The Descent '' Marcos Siega Elizabeth Craft & Sarah Fain January 27 , 2011 ( 2011 - 01 - 27 ) 2J5262 3.55 Stefan tries to contact Isobel and gets in touch with John Gilbert , who comes home . While Damon tries to get Jules to tell him how to cure the werewolf bite , he asks Elena to keep an eye on Rose , who becomes delirious and mistakes her for Katherine . Caroline and Matt confess their love for each other . Tyler 's reaction to Caroline 's generosity surprises her . Rose escapes from the Salvatore house and goes on a killing spree . Damon finds her and brought her back to the Salvatore 's house , he then stakes her , while giving her a peaceful death by giving her a dream about her old home . He confesses to a stranger that he misses being human . He lets her go , but bites her soon after . Jules informs Tyler that she knows that he and Mason are werewolves . She tells him that more werewolves are coming . 35 13 `` Daddy Issues '' Joshua Butler Kevin Williamson & Julie Plec February 3 , 2011 ( 2011 - 02 - 03 ) 2J5263 3.22 Tyler is furious that Caroline has kept Mason 's death secret from him . Jenna becomes upset over the revelation that John is Elena 's biological father . Jules meets her wolf - lover Brady and tells him she wants to leave town and take Tyler with them . Caroline asks Stefan to reason with Tyler , while Jules takes Caroline hostage . Jules tells Stefan to bring Tyler to her in exchange for Caroline . Stefan tries to make peace , but he fails , and Damon offers his `` bloodier '' method . Jules then calls on her wolf friends , and although Damon and Stefan are outnumbered , they kill most of the wolves. Tyler releases Caroline from the cage , but watches as Jules has Caroline at gunpoint . As Stefan and Damon are about to get staked , Jonas , on Elijah 's behalf , incapacitates the remaining wolves. Tyler tries to apologize to Caroline , but she tells him they are no longer friends . Tyler tells Jules and Brady that Mason was probably killed because he found the moonstone . John says that he returned to protect Elena , and that the only way to kill an Original is with a dagger dipped in ash from a white oak as old as the Originals . John is shown to be still working with Katherine and trying to get her out of the tomb . 36 14 `` Crying Wolf '' David Von Ancken Brian Young February 10 , 2011 ( 2011 - 02 - 10 ) 2J5264 2.78 Stefan and Elena spend a weekend at the Gilbert lakehouse , unaware that they 've been followed by Tyler and Brady . Jenna worries that Alaric is n't being honest about his past . Jules and Brady explain the sun and moon curse to Tyler and lure him into helping them . Bonnie performs a hypnosis spell on Luka in order to get information . Luka reveals that Elijah plans to kill Klaus by making him vulnerable after he sacrifices Elena . He also reveals that Klaus has his sister , so he and his father are working for Elijah to help him kill Klaus . Jules and her friends torture Damon for information about the moonstone , but Elijah intervenes , kills most of the wolves , and saves Damon . Brady finds Stefan and shoots him with a wooden bullet , leaving Tyler to guard him . When Tyler learns that Elena has to die for the curse to be broken , he lets Stefan go . Stefan kills Brady to save Elena . Meanwhile , Jeremy and Bonnie confess their feelings for each other and kiss . Realising that Elena knew about Elijah 's real plan for her , Stefan tells her that she is behaving like a martyr. Tyler tells Matt that he has feelings for Caroline but knows that Caroline loves Matt . The episode ends with Jules and Tyler leaving town . 37 15 `` The Dinner Party '' Marcos Siega Andrew Chambliss February 17 , 2011 ( 2011 - 02 - 17 ) 2J5265 3.07 Elena reads one of Jonathan Gilbert 's journals about a night when Stefan attacked him and killed two of the Fells . Stefan admits that he had been brutal and inhuman until Lexi showed him the path of love and humanity . Damon invites Elijah to the boarding house for a dinner party , intending to kill him . Jonathan Gilbert 's journal reveals that if a vampire uses the dagger to kill an Original , both will die . After Stefan sends a warning , Alaric stabs and kills Elijah , but the body later disappears . Elena reads in the journal that if the dagger is removed , the Original will come back to life . John blackmails Alaric into returning his ring . Elijah shows up at the lake house telling Elena that the deal is off , but Elena threatens to kill herself and become a vampire so that she will no longer be useful to him . Elijah calls her out on a bluff , but Elena stabs herself . Elijah begs Elena to let him heal her , and she agrees , but then stabs him with the dagger , killing him again . Damon returns home to find Katherine there . Elijah 's compulsion on her has worn off with his death , and she says she intends to help them . 38 16 `` The House Guest '' Michael Katleman Caroline Dries February 24 , 2011 ( 2011 - 02 - 24 ) 2J5266 2.98 Discovering that Katherine is free , Elena is upset . Stefan and Bonnie try to persuade Jonas and Luka to work with them , but Jonas wants Elijah alive again . He performs a ritual that puts Luka in the boarding house in invisible form . Luka tries to remove the dagger from Elijah 's body , but Katherine stops him . Luka then stakes Katherine , but Damon uses a flamethrower to prevent the removal of the dagger . Luka is fatally burned , and Jonas vows to avenge him by killing Elena . Bonnie tells Elena about her relationship with Jeremy and is surprised by Elena 's positive response . Jonas appears at the Grill , looking for Elena . Bonnie tries to stop him , but he disables her ; Matt intervenes , but Jonas stabs him . Caroline sees Matt dying and forces him to drink her blood to save his life . Jonas attacks Elena , but she proves to be Katherine , and she bites him . Alaric tells Jenna that he loves her . Bonnie reveals that Jonas has restored her powers and told her how to kill Klaus . Caroline tells Matt that she is a vampire , but he takes the news badly . Isobel shows up at Elena 's house and tells Jenna that she is Elena 's mother . 39 17 `` Know Thy Enemy '' Wendey Stanzler Mike Daniels April 7 , 2011 ( 2011 - 04 - 07 ) 2J5267 2.73 Elena and Alaric become angry with John when Isobel 's arrival devastates Jenna . Alaric is abducted by Maddox , a warlock from Klaus 's inner circle . Meanwhile , Bonnie works with Jeremy and Damon to find the spell they need to gather the power of the witches killed in the massacre . Damon takes them to the site where the witches were burned . Matt demands to know what happened to Vicki . After Caroline tells him and then compels him to forget , it is revealed that Matt 's involvement was a setup by Sheriff Forbes to find out everything about the vampires . Matt has drunk vervain , so the compulsion does not work . Isobel kidnaps Elena and then receives a phone call from Maddox , who tells her that she has finished what Klaus compelled her to do and is free to let Elena go . Isobel apologizes to Elena for being a disappointment as a mother , removes her necklace , and burns to death in the sun . Stefan and Damon realize that Bonnie is their new secret weapon since she now has tremendous power . Jeremy is upset because , if Bonnie uses too much power , she will die . Katherine , who had been set up by Isobel and taken by Maddox , wakes up to see Klaus take control of Alaric 's body . 40 18 `` The Last Dance '' John Behring Michael Narducci April 14 , 2011 ( 2011 - 04 - 14 ) 2J5268 2.81 Klaus ( in Alaric 's body ) compels Katherine to tell him how the others plan to kill him . He then finds out that Bonnie has obtained power that could threaten his life . At the school dance , Jeremy confronts Bonnie about why she wants to kill herself for Elena , and Damon overhears . Jeremy goes to Stefan for help , and Stefan tells Elena about Bonnie 's plans . Elena finally guesses who `` Alaric '' really is . Bonnie fights Klaus with her powers and appears to die . As Elena grieves , Damon tells her that Klaus must believe Bonnie is dead , but her death was faked . Realizing that Bonnie intends to endanger herself to defeat Klaus , Elena pulls the dagger out of Elijah 's heart . 41 19 `` Klaus '' Joshua Butler Kevin Williamson & Julie Plec April 21 , 2011 ( 2011 - 04 - 21 ) 2J5269 2.70 After Elena removed the dagger , Elijah wakes , and Elena makes another deal with him . In a flashback to 1492 England , Katherine meets Elijah and Klaus for the first time . Elijah and Klaus were raised as brothers , but Klaus was the result of their mother 's affair with a man from a werewolf bloodline . Elijah 's father hunted down the man and had him and his family killed , beginning the schism between werewolves and vampires . As a vampire / werewolf hybrid , Klaus can only be killed by a witch . The sun and moon curse was fake -- the real curse is that Klaus 's werewolf side had been forced into dormancy by witches . Jenna finally finds out about the vampires from Stefan and Klaus / Alaric . Elsewhere , Katherine is being held captive by Klaus . Damon finds her and gives her a vial of vervain to protect her from further compulsion . At the end of the episode , Maddox and Greta ( Luka 's sister ) perform a ritual to release Klaus 's spirit from Alaric 's body and put it back into his own . 42 20 `` The Last Day '' J. Miller Tobin Andrew Chambliss & Brian Young April 28 , 2011 ( 2011 - 04 - 28 ) 2J5270 2.68 Elijah tells Elena that the way to break the curse involves sacrifice a vampire and a werewolf . Maddox injures Carol Lockwood to make Tyler return to town , after which he and Greta kidnap Caroline and Tyler . Damon forces Elana to drink his blood so she will `` survive '' the sacrifice . Alaric returns as himself and gives the message from Klaus that the ritual will happen that night . Jenna forgives him . Damon realizes that if Klaus does n't have a werewolf , he will be unable to complete the ritual , and Elena will have another month . He rescues Caroline and Tyler from the tomb and kills Maddox . Klaus takes Elena from the boarding house to begin the ritual . Damon informs Klaus that he has rescued the vampire and werewolf he needs for the ritual , but Klaus says he has backups . At the site of the ritual , Elena realizes that Klaus has turned Jenna and is using her as the vampire . Katherine makes Damon aware of a wolf bite he got from Tyler during his transformation . 43 21 `` The Sun Also Rises '' Paul M. Sommers Caroline Dries & Mike Daniels May 5 , 2011 ( 2011 - 05 - 05 ) 2J5271 2.84 Matt and Caroline are in the Lockwood cellar while Tyler , in wolf form , attacks them , and they hide . Meanwhile , Greta the witch feeds Jenna her blood , completing Jenna 's transformation into a vampire . Elijah is revealed to be seeking revenge on Klaus for killing his family and burying their bodies at sea . Klaus begins the ritual and kills Jules , the werewolf . Stefan offers to switch places with Jenna , but Klaus refuses and kills her . Bonnie performs a spell that can bring someone back to life by joining two people 's souls , binding John and Elena . At the ritual grounds , Klaus drains Elena 's blood and begins to transform . However , Bonnie uses her powers to weaken him while Damon kills Greta . Before Elijah can rip out his heart , Klaus says he did n't bury the bodies at sea and if he is killed , Elijah will never find them . Elijah listens to him and flees with Klaus . When Elena comes back to life , John dies . At Jenna 's and John 's funeral , Damon reveals to Stefan that he was bitten by Tyler and asks him to not tell Elena . 44 22 `` As I Lay Dying '' John Behring Turi Meyer & Al Septien & Michael Narducci May 12 , 2011 ( 2011 - 05 - 12 ) 2J5272 2.86 This episode 's plot summary may be too long or excessively detailed . Please help improve it by removing unnecessary details and making it more concise . ( November 2016 ) ( Learn how and when to remove this template message ) Damon apologizes to Elena for feeding her his blood . At home , he tries to kill himself by taking off his ring and walking into sunlight but is stopped by Stefan and locked in a cell . Klaus has completed the transformation into a wolf and awakens to find Elijah waiting for him . He makes Klaus remember his deal : he must reunite Elijah with their family , and Klaus does so by staking Elijah . Stefan seeks Klaus for a cure for Damon . Klaus then bites Katherine and feeds her his blood , revealing the cure for a werewolf bite . In exchange for a vial of his blood , Klaus wants Stefan to become a ripper again and leave Mystic Falls with him . Stefan drinks human blood to prove himself . Klaus gives Katherine the cure for Damon and allows her to leave . Sheriff Forbes , who wants to kill Damon , accidentally frees him from his cell . She later tracks him down and shoots at him but strikes and kills Jeremy instead . Bonnie begs the witches to bring Jeremy back to life saying that she loves him , and they do , warning of `` consequences . '' Elena finds a delirious Damon , brings him home , and kisses him after he confesses his love . Katherine interrupts with Klaus 's cure for the werewolf bite . Klaus tests Stefan , asking him to kill someone . Once Stefan does , Klaus says that they can leave Mystic Falls . At the Gilbert house , Jeremy finds his deceased vampire ex-girlfriends Anna and Vicki .

Question: what episode does caroline get turned into a vampire
Answer: The Return