The third book deals with Elena’s adjustment to her vampirism, as well as her confusion at loving both brothers. Stefan finds Elena dead, and believes that the force that was chasing Elena was Damon. They fight, and in the middle of it, Elena awakens, and attacks Stefan— as Damon had given Elena more of his blood in the exchange and as such viewed Stefan as a threat to her creator. They stop the fight, Stefan is broken-hearted assuming that her attack on him meant she loved Damon more, and Damon tries to clear everything up, being very nice and rational to Elena.
Still caring for Elena whether she loved him or not, Stefan convinced Matt to feed Elena blood to help her, leaving Matt in shock because of what she had become, as well from discovering Stefan had almost killed Tyler and his buddies, leaving Caroline unharmed. Damon left Elena in the attic of Robert E. Lee’s history teacher for her safety and she awoke days later to stumble across her own funeral reception.
After reading her diary, Elena’s memories returned clearly and was overjoyed and relieved when Stefan forgave her. But the Other Power was taking control of the animals in Fell’s Church, driving many to dispose of their pets. Elena convinces the brothers to work together to stop this powerful force.
While having to stay out of the way of the town’s new vampire hunter (the new teacher, Alaric Saltzman), Stefan, Damon, Elena and her friends search for the source of the dark presence that has overtaken the town and which they also suspect to be behind Elena’s death.
They find the answer in Honoria Fell’s tomb, and it turns out to be Katherine, who in fact did not die centuries before as the brothers had thought. Instead, she had faked her death, having her maid bring ashes from the kitchen, lay them out on her dress, and put her lapis lazuli ring on top, while she had another forged, making it looked as if she had killed herself.
Since then, Stefan has lived with the guilt of her death, while Katherine has spent that time seething with anger. She decides to take revenge, and is jealous of Elena for “stealing” both brothers’ love. Katherine reveals that she is the one who attacked Vicki and ran Elena off the bridge.
They are all tortured brutally, and Elena ends this by knocking Katherine into the light of the tomb, while unsuccessfully getting herself out of the sunshine fast enough. She dies in the end, saying that she wants both brothers’ words that they would take care of each other because Damon is often misunderstood, and she wants the fraternal rivalry to end, also telling Stefan that she loved him, and that she did not want this to happen, causing pain for him as Katherine had.