There was Masquerade in Mystic falls. Of course you (Katherine) had to come to provocate everyone. She stepped in in black dress and mask on, her hair loosened and was pretending to be Elena, who was inside. She went upstairs to steal the stone that can turn you into human again but she didn't know that Damon noticed her

After he realised he pinned her against the wall by force as fast as light holding her throat and pointing wooden rod at her

"Katherine"

*He whispers and she just smirks