<P> Back at the tomb, Katherine continues her story; 1492: Katerina stabs herself because she prefers to die than go back to Klaus . Rose does not let her die and gives her her blood to heal her when Trevor arrives and tells Rose that he loves Katerina and he wants to help her run away . While Rose tries to talk sense to him, Katerina gets the opportunity and suicides, triggering her own transformation to a vampire since she knows that as a vampire she would be useless to Klaus . </P> <P> Katerina wakes up a little later and Rose and Trevor realize that she used both of them to achieve her goal; become a vampire . Rose tries to stake her but Katerina gets away . Back on the present, Elena is shocked that Katherine killed herself and ruined Rose and Trevor's lives but Katherine says that everything she did was to protect herself, something she will always do . Elena guesses that Katherine's return was to hand her over to Klaus something that Katherine does not deny . Elena asks what else is needed to break the curse and Katherine says: a doppelganger (Elena), a vampire (Caroline), a werewolf (Mason but since Damon killed him, she turned Tyler), a witch (Bonnie) and the moonstone . </P> <P> Luka gets back to the Grill to apologize to Bonnie for his father's earlier behavior and he also reveals that he and his father are warlocks who just try to fit to their new home . Bonnie believes him and the two of them start talking and getting closer, while Jeremy watches from afar . </P> <P> Stefan figures out where Elena is and gets to the tomb . He tells Elena that whatever Katherine told her is a lie because she is a liar and that he will do everything to protect her . Katherine interrupts him to tell him that Elena is doomed and he cannot do anything about it . She finishes her story by telling them that when she run away, Klaus went to her home and killed everyone she loved . She reassures them that Klaus will do the same to Elena's family and friends if he cannot get to her . Katherine offers them the moonstone but Stefan accuses her that she only gives it to them to trade it with her freedom but Katherine points out that her being trapped in the tomb makes her the safest vampire in town when Klaus comes to kill everyone, since he won't want to get into a tomb where he will not be able to get out . </P>

When do you see katherine in vampire diaries