And though it may not have given a clear answer as to how Benedict Cumberbatch’s Sherlock Holmes faked his own death it did draw viewers - more than nine million in total.
How I See It
Gareth Thomas, founder, Capella
The BBC played this one well, seeding just enough content to fuel the fan-based buzz, without oversaturating audiences.
It must have been tempting to reveal more snippets - Derren Brown cameo? - but the Beeb did well to limit its teasing and avoid the disappointment that was inevitable after the massively over-hyped Dr Who 50th anniversary episode.
The choice of media was smart and efficient for the enormous target audience, spread across 200 territories.
As far back as May 2012 the writers started drip-feeding snippets of information on Twitter and hinting at series three plot twists.
The release of the seven-minute prequel across digital platforms was inspired - it was shared widely, and achieved more than five million views on YouTube.
The BBC also teased via the John Watson and Sherlock blogs but didn't need to do much more - it just left it to the fans.
Traditional media weren't ignored either, with a slick stunt ensuring broad coverage across entertainment media and the show's writers, producers and talent all giving interviews.
Review and news teams were sufficiently informed and excited to write a slew of positive articles that will ensure the crucial catch-up audience doesn't disappoint.
It was also fascinating to see the real and fictional worlds converging around the show, with fictional fans tweeting within the show using a hashtag then adopted by real-world fans.
Maybe we'll see more use of newer social platforms in the next series, perhaps even in real time - snapchat clues in a live episode anyone?
All in all, a smart, integrated campaign that like the series itself left fans guessing, speculating and even doing some deduction of their own.