7 Reasons Sherlock Series 4 Should Be The Last

WARNING: This section contains spoilers for events in the original Holmes stories and wild speculation about the show.

When a publicity photo for series four was released a few months ago, fans were immediately aghast at how white Martin Freeman’s hair was. Set photos have indicated that this wasn’t just a trick of the light and the good doctor will be visibly (albeit subtly) aged in the upcoming series. Plus he’s carrying a baby, so there's that.

So we know that Watson starts the series with a wife and baby, but that may not be how he ends it. In the original 'Sherlock Holmes' stories, Mary Watson (nee Morstan) has a very short lifespan. Shortly after Holmes's resurrection, Mary goes off to meet her maker and John returns to Baker Street. Combined with comments from Freeman's on (and off) screen wife, Amanda Abbington, about her "golden wrap" -- a term typically used for actors who don't think they're coming back -- we're starting to think Mary may end up going the same way

So either Doctor Watson ends the series with a loving wife and baby, whom a sensible man like John won't put in harm's way. Or Mary bites the dust, John is distraught and pledges to protect his child. Either way, palling around the criminal underworld with his former flatmate would come in at a low priority.

There are plenty of Holmes stories that explore an older Holmes and Widower Watson, but that's not the story we've been following. If the show wants to delve into that era, it would make sense to wind down after series four and return in a few years for a more reflective look at the Holmes and Watson dynamic.