Life-long Sherlock fans will already be wide-eyed. But Sherlock and his viewers are only just learning to fear this particular name.
Professor Moriarty. James Moriarty. Jim Moriarty.
He's probably the literary inspiration behind every evil genius and criminal mastermind of the past century. Now he's back to reclaim his crown.
Every hero needs an arch-enemy. In childhood, Sherlock assigned the role to his brother, Mycroft. It may be the only thing he got wrong in his life.
His nemesis has just played his hand and the great game has begun. Holmes versus Moriarty was, is and always will be a legendary clash of minds; only the loser does not get to walk away.
Only the elite may play this game. The pawns are real life people. The puzzles are deadly. Walking away is not an option. Failing to solve the case could well prove fatal.
So yes, not a good day for Sherlock and John, though the former appears to be enjoying the challenge. What neither have quite grasped is that this is all building towards a grand finale, which Moriarty is playing to win.
If all of the episodes of Sherlock have been good so far, this raises the standard to a whole new level. Yes, it is gripping; but only if we're going to raise the bar on the word 'gripping' too!
As befits an epic episode, this story draws upon not one but several canonical sources, all penned by Sir Arthur Conan Doyle. They are: A Study in Scarlet, The Adventure of the Bruce-Partington Plans, The Adventure of the Naval Treaty, The Five Orange Pips, The Adventure of the Retired Colourman, The Adventure of the Final Problem and A Scandal in Bohemia.