
That sense of indulgence and knowing it is a big deal does come through – not heavily perhaps, but I did find it hard to shake. This sense of it not really working, and not really doing much for the viewer also means that, while it is funny and entertaining, it does feel like it is overly pleased with itself at the same time.

The time-hopping doesn't help the actual mystery which is the focus of most of the time, nor does it really fit in the modern setting either. And it is fun, in a way, although it is also heavy with flaws and weakness. It also gives them a chance for a bit of fun away from the modern settings. This jump back in time allows the writers to not have to worry too much about where/how to advance the Moriarty plot, while at the same time appearing to advance it. In the jump back in time, we enter Sherlock's mind as he tries to solve a similar mystery he read about. There is a sense of both these things with this episode, which occur in the few minutes that the plane takes to turn around and land so that the banished Sherlock can deal with the apparent return of Moriarty. As part of this as well, it must be tough for the writers, as they are trying to write an ongoing story without knowing when/if they will get the next episode.

I guess there was also the risk that this amount of effort, and the fact that the stars no longer really 'need' Sherlock as a vehicle, means that there is a feeling of them doing the viewer a favor. I remember feeling that season 3 was a bit too pleased with itself for my tastes, and this is magnified here, where lots of increasingly famous and successful people are crowbarred into place to deliver this episode – and to be fair it must have taken a huge amount of schedule balancing to make it happen, so credit for that. Season 3 of this show already saw it confirmed as 'event television', and there is a greater feeling of that with this first episode to what IMDb calls 'season 4' although it has been a year and a half since the last 'season' ended, and will reportedly be that again before we see another episode.
