 What role does Doc play in conjunction with Sandra?
Her last assignment had been to interview the pilot pair riding the first American manned circum-lunar satellite—and the five alternate pairs who hadn't made the flight. "I heard the Russians have been programmed—with hypnotic cramming and somno-briefing. Sandra's chief difficulty was that she knew absolutely nothing about the game of chess—a point that she had slid over in conferring with the powers at the Space Mirror , but that now had begun to weigh on her. Doc's ability to interpret her mind was as comforting as the bubbly, mildly astringent mixture she was sipping. The equivalent of those in the Machine is the directions fed into it before it plays a game."
 He explains to Sandra how the chess machine works and what the significance of each human chess player is.
 He explains to Sandra that living human personality is key for beating the machine.  He shows Sandra around the tournament.  He explains to Sandra how the chess machine works and what the significance of each human chess player is.  He explains the history of chess scandals to Sandra.