"Damon knelt down, and I rushed toward his side. Katherine was lying on her back, ropes binding her arms and legs. The ropes must have been covered with vervain, because there were terrible burns on the patches of skin that touched the twine. A leather mask covered her face, and her hair was matted with dried blood.
I stood back, not wanting to touch her or even look at her, as Damon set to work untying the muzzle. Once she was free, I couldn’t help but notice her teeth, her fangs, her true nature, obvious in a way I’d never seen before. But Damon was gazing at her as if in a trance. He gently brushed the hair off her face and slowly leaned in to kiss her lips.
“Thank you,” said Katherine simply. That was it. And watching them, the way Katherine’s fingers stroked Damon’s hair, the way Damon cried into her collarbone, I knew that this was true love."
-The Vampire Diaries: Stefan’s Diaries #1: Origins