But the success of the show doesn't depend on its balance of Holmes mythology and contemporary flourishes—it's the strong writing for the two remarkable leads: Benedict Cumberbatch, who used the show as his Hollywood calling card, and Martin Freeman from The Hobbit, the original The Office, and elsewhere. The show is really about the friendship between these two unlikely partners. Despite what Moffat said about the importance of "adventure," the show understands that it's not actually what's engaging; the first episode of the third season, which aired in the US last weekend, wasn't compelling for its mysterious terrorist plot or its missing person impossibilities—it was for the interpersonal drama brought about by Holmes's return to London after faking his suicide, which Watson didn't know was fake. (As in the Conan Doyle stories, Holmes seemed to fall to his death, though in the series it was from a hospital roof, not the top of Reichenbach Falls.) The long and funny scene in which Sherlock surprises the mournful Watson, deeply damaged by the "death" of his companion, was riveting, as was the difficult process of putting their partnership back together.
If you're not caught up, all six episodes of the first two seasons are on Netflix, but they're a little trickier to marathon than your average TV series: each episode is 90 minutes, the series more like a film franchise released in clumps; you could easily consider that first episode of the third season to be Sherlock VII: The Empty Hearse. The second episode airs this Sunday, and the third and final episode the Sunday after that—Sherlock is always over almost as soon as it began, but for a few weeks it's the best thing on TV.
Follow Henry Stewart on Twitter @henrycstewart