The finale of BBC crime drama Sherlock‘s long-awaited third season, “His Last Vow,” will air on the UK on Sunday, but a lucky few people got to see it early during a BAFTA screening and Q & A panel with writer Steven Moffat and producer Sue Vertue. The episode sees Sherlock (Benedict Cumberbatch) and John (Martin Freeman) going up against nefarious blackmailer Charles Augustus Magnussen (Lars Mikkelsen), “the worst man in London,” whom Sherlock hates with a passion.

The character is taken from one of the later Arthur Conan Doyle stories, titled “The Adventure of Charles Augustus Milverton,” and the character has already made two brief appearances this season: once in a quick and sinister scene at the end of “The Empty Hearse,” and the second time in a telegram sent to John and Mary on their wedding day that was simply signed “CAM.”

Despite dedicating an entire episode to the aforementioned wedding, Moffat and Gatiss are apparently far from running out of ideas for the show. Bleeding Cool reports that Moffat repeated assurances during the Q & A that a fourth season is definitely on the way and added, “we’ve already plotted out series four and five.”

[Update: Radio Times now has a more complete transcript from this part of the Q & A]

“Rather excitingly, Mark and I, for no particular reason, we just got out of the rain and sat at the top of the [Sherlock] production bus… and we just started plotting out what we could do in the future. And we plotted out the whole of series four and five.

“So we have got plans – but our plans don’t tend to be ‘Let’s blow up the world or cast the most famous person in the world.’ They tend to be ‘What exciting twists and turns can we add to this?’ And I think we’ve got some crackers! The ideas we had that day, I thought were the best we’ve ever had.”

One of the great things about Sherlock is that it has an enormous wealth of source material upon which to draw, with many cases that can be spun on their heads and reinvented for the modern world. While arch-villain Moriarty was thoroughly thwarted at the end of the second season, Doyle’s character dealt with many crimes and mysteries over the course of his career and any one of them could make for exciting television.

Pending any decisions to expand the length of each season, this only means that Moffat and Gatiss have plotted six episodes ahead. Still, since each episode is 90 minutes long that’s a whole lot of planning. Given the ever-growing success of the show it’s hard to imagine the BBC refusing to green light at least a couple more seasons but, as was the case with the recent hiatus, the real challenge will be making the filming fit into Freeman and Cumberbatch’s schedules.

Some of the more classic cases have already been worked into Sherlock‘s previous episodes, while others have taken place off-screen, but tell us in the comments which other adventures from Doyle’s stories you’re hoping have been included in Moffat and Gatiss’ plans.

Sherlock season three concludes in the UK with ‘His Last Vow” on Sunday, January 12, on BBC One. The season premieres in the US with ‘The Empty Hearse,’ airing on Sunday, January 19, on PBS.

Source: Bleeding Cool, Radio Times