He is the most formidable and menacing enemy Sherlock Holmes has yet encountered: a manipulative media mogul who knows the secret weakness of every eminent politician in Britain.
The introduction of evil press baron Charles Augustus Magnussen in tonight’s blockbuster BBC1 drama is likely to raise parallels with real life, following years of revelations and debate over the links between newspaper owners and the Government.
But while the legendary detective battles with a blackmailer and extortionist with a mental prowess to match his own, he also faces betrayal from someone he considers an ally.
We will reveal no further details of the plot to avoid spoiling the twists and turns for the ten million viewers expected to tune in at 9pm tonight.
But amateur sleuths are already considering the clues from the two other episodes in this short series, to try to deduce which key character could turn out to be not what they appear.
It may be more than a three-pipe problem...
Possibilities include Sherlock’s brother, Mycroft, a senior official in the British Secret Service, played by series co-writer Mark Gatiss, who has referred to himself as the detective’s ‘arch enemy’.
He often plays down his own influence but Sherlock, played by Benedict Cumberbatch, has been heard to say his brother ‘is’ the British Government.
They share a high intelligence and an arrogant streak, but Mycroft has been seen to show a caring side and demonstrates concern for his brother.
Dr John Watson is Sherlock’s sidekick and best friend, with the detective acting as best man at his wedding to Mary Morstan in last weekend’s episode.
Holmes and Watson share an incredibly close bond, but Watson, played by Martin Freeman, was furious when he discovered Sherlock had faked his own death and left him to grieve for two years.
Other members of Sherlock’s close circle include Detective Inspector Lastrade, the officer played by Rupert Graves, who relies on him for help with many of his cases despite often being infuriated by his behaviour, and Philip Anderson, a forensics expert played by Jonathan Aris, who accused Sherlock of being a conman before becoming an almost obsessive fan of the detective.
Or what of Mrs Hudson (Una Stubbs), Sherlock’s landlady at 221B Baker Street, who offers the detective a reduced rent after he ensured the conviction and execution of her ex-husband in Florida? Or Molly Hooper (Louise Brealey), a pathologist with an infatuation for Sherlock which he regularly exploits in order to be able to examine the dead bodies of victims? She was one of the few people who knew that Sherlock had faked his own death.
Fans have already begun speculating on the meaning of the episode’s title His Last Vow, with previous episodes’ titles providing key clues to the forthcoming events.
One thing that can be confirmed is the producers’ plans to continue the drama for a fourth and fifth series.
Co-writer Steven Moffatt has confirmed he and Gatiss had already mapped out their plans for subsequent storylines.
He said: ‘We’ll be back. We have got plans, exciting twists and turns, and I think we’ve got some crackers.’
Filming could begin on the upcoming series as early as this summer, with producers currently trying to arrange schedules to accommodate Cumberbatch and Freeman.
But first Sherlock must defeat the fiendish Magnussen, played by The Killing star Lars Mikkelsen. As the detective says: ‘I’ve dealt with murderers, psychopaths. None of them can turn my stomach like Charles Augustus Magnussen.’
update: my title was correct