Kit thinks to herself that Nat is a "contradictory person." What is it about Nat that she finds contradictory?

From the text:

What a contradictory person he was, she thought, hurrying along South Road. Always putting her at a disadvantage somehow, and yet, now and then, surprising her, letting her peek through a door that always seemed to slam shut again before she could actually see inside. She would never know what to expect next from him.