The creators of BBC1 hit Sherlock have given fans a teaser about the detective show's third series, due to begin filming next January, revealing the three words "rat, wedding, bow".

Steven Moffat and Mark Gatiss, and Sherlock producer Sue Vertue, revealed the cryptic clues at a masterclass session on the popular and critically acclaimed BBC1 drama at the MediaGuardian Edinburgh International Television Festival on Friday afternoon.

"We have three new words – which may be misleading, are not titles, are only teases or possibly clues, but might be deliberately designed to get you into a lather. Who knows?" said Moffat.

There is no broadcast date for the new instalments as yet.

The second series of the modern day version of Arthur Conan Doyle's detective stories ended on a cliffhanger, with Benedict Cumberbatch's Sherlock Holmes apparently falling to his death from a building, before appearing by his own graveside.

Fans have been gripped by fevered speculation about how Holmes had faked his own death, with viewers putting forward complex theories. "Some of them are incredibly byzantine, which is amazing and it's funny and lovely that people could be so elaborate about it," said Gatiss.

"[But] you can't possibly build a solution on something that can only be glimpsed when you blow up the image 65 times and then discover a continuity error."

Moffat revealed that Sherlock's creators had already decided how the puzzle would resolve itself when they began season two. Although, the writer teased, "That doesn't mean we won't change it of course …"

Asked what the secret of Sherlock's success was, Moffat said he put it down to love. "It sounds awful and sentimental – but it's love. We love Sherlock Holmes so much, we're so obsessed with it. This is fan fiction.

"It is an exercise in love. We wouldn't have minded if nobody had watched it, if we'd been allowed to carry on making them for each other."

Instead, however, more than 8 million viewers tuned in to the show – taking its team by surprise. "We thought it would be an audience of 4 million and an obscure award from a Polish festival. We thought it would be about that level," said Moffat.

The writer, a canny promoter of his shows Sherlock and Doctor Who, had stoked speculation about the three words he'd give fans, with a tweet on Thursday: "Last year it was Woman, Hound, Fall," tweeted Moffat earlier today. "This year's three words revealed tomorrow at#MGEITF #Sherlock Master Class."

Moffat admitted at the Edinburgh TV festival session on Friday that he had got two of the three words wrong – they were actually Adler, Hound and Reichenbach.

Gatiss has already confirmed that the opening episode of the new series will be at least partly based on The Adventure of the Empty House, in which Sherlock Holmes returns after cheating death at the hands of professor Moriarty at the Reichenbach Falls.

In series two, Hound was based on The Hound of the Baskervilles, while

Adler was an updated version of A Scandal in Bohemia. The film prompted controversy by featuring actor Lara Pulver, playing Irene Adler as a dominatrix who appeared almost naked in one scene.

And today Gatiss revealed that Pulver's audition tape also suggested she was naked. "She also made everyone sit up because she sent a tape from LA and she didn't have any clothes on," he said – although Moffat added that he was sure she was wearing a towel.