June 9, 1870. Charles Dickens sat writing at his desk. He had been laboring more than was his custom on his latest book. Though the story was progressing well, Mr. Dickens was not feeling well. His left hand clawed at the air. His left foot dragged on the ground. And though he had recently retired from public performances with a final reading from Pickwick, his pen scarcely ceased its scratching. A profound and perplexing mystery was unfolding beneath that pen and Mr. Dickens’ knew it well. If only his readers might know it as well.It had been five years...