"The Adventure of the Empty House" marks Sherlock Holmes's return after his supposed death at the Reichenbach Falls. Dr. John Watson, still grieving Holmes's loss, is astonished when Holmes reveals himself to be alive. Holmes explains how he survived and has been in hiding, pursuing his own investigations. Together, they unravel a murder plot involving Colonel Sebastian Moran, a former associate of Professor Moriarty. Holmes ingeniously traps Moran, thus resolving the case and affirming his return to active detective work.