The baby vampire & the new werewolf take advantage of her maker's "distraction" over the moonstone situation. To be perfectly honest, missery suits them (as "I'm only happy when it rains" goes) and, for two creatures who only smile in the dark, they take upon themselves the task to make Tyler's first transition as smooth as possible. Although Mason's journals make things look A LOT worse than Tyler originally thought, Caroline sticks to him. In, what is perhaps one of the most moving scenes of the entire show, she explains what it was like to be alone when she first turned, to have no control over her own urges, to be responsible of killing a man. She vows not to let that happen to Tyler, she's not going to leave him alone.
The irony being that the baby vampire is braver than her own maker, for Damon is not going to go inside the tomb without his "crafty little witch", a couple of baby brothers and at least a dozen different spells that could have killed Bonnie, if it weren't because Jeremy and Luka are not going to leave her on her own either. It's because of this latest stunt to save Elena that Stefan gets trapped inside that tomb ...with Katherine.