Holmes return glance is on the order of: Yes, I'm sure. Be prepared for vigourous cross-examination.
Holmes smiles and bends back down. "I shan't hurt you Winky. You have my word of honour. I've no doubt you've heard various things about muggles and are therefore somewhat apprehensive. But it is a very grave mistake to assume things before you have any knowledge of them. I invite you to ask any question that occurs to you and I shall do my very best to answer it." He stands up. "Shall we begin with the kitchen?" He doesn't hold out his hand to her, but Holmes' tone makes it clear that it is extended metaphorically.