Stealth and Troubled Pleasure

What really happened at Reichenbach Falls? What was the true nature of the relationship between Sherlock Holmes and Professor Moriarty? Dr. Watson's version of the events is true as far as he knew, but now, at long last, Hilda Adair breaks her silence.
Hilda appears once in "The Adventure of the Empty Room," an incidental character in Watson's re-telling. She opens the door, finds her brother Ronald shot dead, and vanishes from "the canon."
But she was not a bystander in the story of Holmes and Moriarty. They were bystanders in hers.