"Bodies naturally work out splinters," the Doctor says, approving of the connection. "And you'll naturally work him out. Your body is tougher than he is. He's nothing but a remnant of what he was."

He wants to comfort her, but he doesn't know how. He's terrified to be too close, to make the Master that much more ingrained in her. If the Master were a metallic splinter, he'd be the exact opposite of the Doctor's magnetism, pushing deeper into her if he got too close.

"It will be all right," he promises.