- In Bulgaria in 1490, Katherine gave birth to a daughter. Her disappointed family immediately took the child away from her and banished Katherine. She ended up in England.
- In 1492, she got close to someone named Klaus, before learning he was a vampire and also learning he wanted to kill her because she's a Petrova doppleganger and her blood can help break the sun and moon curse. Katherine befriended another vampire named Trevor, who helped her escape, telling her to go to his friend Rose's house.
- Rose welcomed Katherine in, but then locked her in a room and planned on giving her to Klaus because she feared his wrath. But when Katherine stabbed herself because she claimed she'd rather die on her own than be sacrificed, Rose gave her blood to keep her alive. From there, Trevor arrived, Rose left the room - and Katherine hung herself, well aware it would turn her into a vampire.
- This was her plan all along, as Klaus needed a human doppleganger to sacrifice. Katherine proceeded to leave Rose's place, which is what led to Rose and Trevor being on the run, for helping her in the first place. Katherine has also been on the run this whole time, but returned to Mystic Falls because she wanted to finally strike a deal with Klaus. She was willing to gather all he needed to break the curse - a doppleganger, a vampire, a werewolf, a witch and the moonstone, which she possess in the tomb - in order to hand them over and finally be free.
- Damon bonded with Rose, who explained how she found Elijah: via a contact in Richmond. Off they went to a special vampire coffee shop with double-paned windows and that's where they met Slater. He had spent eternity getting degrees and seemed like a helpful guy. But before he could reveal too much, Elijah showed up outside and broke through the unique window. All the vampire fled, with Damon pulling Rose to safety.
- Late in the episode, he and Rose slept together.
- Bonnie befriended a new student named Luka, much to Jeremy's flirtatious chagrin. He introduced her to his father, Dr. Jonas Martin, who quickly asked if she had relatives in Salem. The reason, Luka later explained? They were warlocks and his dad just wanted to feel her out.
- But there's more to it: the episode concluded with Slater calling Rose and telling her and Damon they could make it so that neither werewolves nor vampires ever broke the curse. But they'd need a witch and they'd need the moonstone. After he hung up, we learned that Elijah compelled him to make the call... and then to stake himself. Pan out, and we also see Dr. Martin come into the room behind Elijah. These two are working together.
Source: TV Fanatic