"I know you have little reason to trust us, Granger, but if I wanted to kill you, it would be easy in your condition.  I would hardly bother with poison." He took a small piece of the cheese and ate it himself.  The goblet of water magically refilled.  At last, she gave in, and ate a little, slowly and painfully, as he rose, busied himself for a moment at a cabinet nearby and returned with a small phial.