Corrected entry: Bonnie uses some magic, a map and Jeremy's blood to try and locate the captured Elena. She states that, because Jeremy and Elena are blood-related, the spell will work. However, we know from previous episodes that Elena was, in fact, adopted and is not blood related to Jeremy. The spell, however, still works and they find Elena's location. (00:10:05)
Corrected entry: At the end of the episode, Katherine brings the cure to Damon and Elena. But she shouldn't have been able to enter the house; Elena hadn't invited her in since the house deed was put in her name.
Correction: Katherine was able to go to the house because the seal didn't work anymore after Elena died in The Sacrifice.
Correction: The spell was successful as Elena's biological father is actually Jeremy's uncle, meaning they are biological cousins as well as adoptive siblings.