<Table> <Tr> <Th> No . overall </Th> <Th> No. in season </Th> <Th> Title </Th> <Th> Directed by </Th> <Th> Written by </Th> <Th> Original air date </Th> <Th> Prod . code </Th> <Th> U.S. viewers ( millions ) </Th> </Tr> <Tr> <Th> 23 </Th> <Td> </Td> <Td> `` The Return '' </Td> <Td> J. Miller Tobin </Td> <Td> Kevin Williamson & Julie Plec </Td> <Td> September 9 , 2010 ( 2010 - 09 - 09 ) </Td> <Td> 2J5251 </Td> <Td> 3.28 </Td> </Tr> <Tr> <Td colspan="8"> 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 . '' </Td> </Tr> <Tr> <Th> 24 </Th> <Td> </Td> <Td> `` Brave New World '' </Td> <Td> John Dahl </Td> <Td> Brian Young </Td> <Td> September 16 , 2010 ( 2010 - 09 - 16 ) </Td> <Td> 2J5252 </Td> <Td> 3.05 </Td> </Tr> <Tr> <Td colspan="8"> 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 . </Td> </Tr> <Tr> <Th> 25 </Th> <Td> </Td> <Td> `` Bad Moon Rising '' </Td> <Td> Patrick Norris </Td> <Td> Andrew Chambliss </Td> <Td> September 23 , 2010 ( 2010 - 09 - 23 ) </Td> <Td> 2J5253 </Td> <Td> 3.57 </Td> </Tr> <Tr> <Td colspan="8"> 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 . </Td> </Tr> <Tr> <Th> 26 </Th> <Td> </Td> <Td> `` Memory Lane '' </Td> <Td> Rob Hardy </Td> <Td> Caroline Dries </Td> <Td> September 30 , 2010 ( 2010 - 09 - 30 ) </Td> <Td> 2J5254 </Td> <Td> 3.18 </Td> </Tr> <Tr> <Td colspan="8"> 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
what episode does caroline get turned into a vampire
The Return