He nearly feels a rush of relief when the other speaks finally, it's true the other is frightened, but the Doctor's thankful to see him feeling anything at all. The strange blankness the other had before somewhat scaring him. "No, you're not.."
He trails off a little when the door suddenly opens, the man that enters bringing an air with him that the Doctor can't quite place. He's cold with a scent of something...chemical perhaps? He can't quite stop the other from injecting his cellmate with the solution, but he does pull him off just as quickly, pressing him against the nearby wall.
He had a slight advantage with his physiology, but he'd never had to exploit it before, it always felt cheap. This time however, he chose to take whatever advantage he could get. He needs answers and he needs them now. His TARDIS is in danger, the young man in the cell with him is in danger...and he can just barely hear the others. This whole place just screams wrong.
"Who are you? What did you do to him?", he asked calmly, though his anger at the man's treatment of the stranger made it hard to remain civil.