The episode is an adaptation of Arthur Conan Doyle's short story : The Adventure of the Empty House (1903).
When Conan Doyle threw his hero into the depths of Reichenbach falls, it was with the firm intention to leave him there for ever. But when he changed his mind, he had to explain why Holmes had, in fact, pretended to be dead. This enterprise was a tricky one, for what was the use of feigning his death, since Colonel Moran, Moriarty's closest friend, knew the detective had survived the fight?