The Doctor returns the stare. He's not sure when or why he's started taking this stuff, but given his history, he can at least make some very good educated guesses. Does he still hear those drums? Considering the hair and the fact he hasn't even died yet in that body, the Doctor thinks he probably does...and okay, so he could tell him the truth about those except it's one of those complicated timey-wimey things. After all, he considers the Master infinitely more complex temporally than River or Jamie, their time travel or their paradoxes aside. It would only take two minutes -- maybe one -- to tell the Master the truth about the end of the Time War. Do the right thing for all the wrong reasons. The petty part of him thinks it'd be worth it to let the man stew in that one.

Instead the Doctor bites it back.

"Generous one, you!" the Doctor says. He tilts his head and watches the Master, not quite sure what he plans to do with that horse of his. It's not in much better shape than his. "I take it this is new. Very new as in Stacy new. Does it help?"