“The lunatic is on the grass. The lunatic is on the grass.” It was an hour before midnight. Ten-year-old James was in his bedroom, alone, when he was suddenly gripped by terror. A Pink Floyd song rang out through the empty room. The radio turned on by itself. “The lunatic is on the grass. The lunatic is in the hall.” James lay paralyzed, locked in that helpless state that is itself as terrifying as whatever causes it. He wanted to move or cry out but couldn’t. So he just listened. “The lunatic is in my head. There’s someone in my...