There are many questions Sherlock fans want answered when the series returns on New Year’s Day. How did Sherlock managed that death-defying leap, for instance. How will he reveal to his friend John that he is not, in fact, dead? And how will John react to the news?
But the world doesn’t revolve around Sherlock (despite what he might think) and another thing viewers will be keeping a close eye on is the dynamic between Martin Freeman's John Watson and his new love interest Mary Morstan.
Freeman’s real-life partner Amanda Abbington plays the "sensible, quick-witted" Mary – and according to their co-star Benedict Cumberbatch, the two are "delightful" together.
“You were delightful with her. Very lovely, really lovely,” Cumberbatch told Freeman during a Q&A at the weekend, eliciting a huge “Aaaah!” from the audience.
Meanwhile, Freeman was keen to make clear that Abbington’s casting had not been the result of his own demands.
“It wasn't a John and Yoko thing where I said ‘I wan't my missus in this',” said Freeman. “I think [co-creator] Mark [Gatiss] and [producer] Sue [Vertue] had thought ‘Who would be a good Mary?’ And Amanda is a really good Mary.
“If she was nothing to do with me she's someone who would definitely have gone up for it – she's there or thereabouts in that casting. Mark had worked with her before, Sue had worked with her before, we all just got on and we knew that chemistry would work."
Sherlock returns to BBC1 with The Empty Hearse at 9pm on New Year's Day