Just as Stefan resolves to let go and pull away, get up off this bed before something happens, she kisses him. That kiss undoes him, and he caves to desire, pushing her back against the mattress with a groan against her lips. The fact that they don't have time for this, shut door or not, escapes him at the moment, too caught up in the feel of her beneathe him, happy to just kiss her and hold her for as long as he's allowed to.