Believed dead after his fatal encounter with Professor Moriarity three years earlier, Sherlock Holmes returns to England to foil a plot to murder him by a former Moriarity gang member.
Holmes is asked by the country's Prime Minister to aid in the recovery of a stolen diplomatic letter, which, if published, might lead England into war.
Holmes is called to a manor house to investigate the brutal murder of a country lord with a fireplace poker and reconcile the story of his bruised and battered wife with the facts.
Inspector Lastrade reveals to Holmes that someone has been inexplicably breaking into homes for the senseless purpose of breaking small busts of Napoleon.
Mary Morstan has received a pearl in the post every year since her father's disappearance; this leads Holmes and Watson to the truth about a secret pact between four convicts during the Indian Mutiny of 1857.