Speaking at the TV panel at Empire Presents... Big Screen, the Sherlock writer opened up about the new run of the BBC drama, which is just "a week and a bit" from completing production.
"Season two is what we're calling 'The Woman, The Hound and The Fall' trilogy," Gatiss said.
"So there'll be a version of A Scandal in Bohemia, a version of The Hound of the Baskervilles and a version of The Final Problem," he explained, referring to author Arthur Conan Doyle's detective stories.
Gatiss had previously confirmed that the second series of Sherlock would be based on these three stories in April.
He went on to speak more broadly about the series, insisting that it is really about an unlikely friendship between two men.
"It's a rare chance to do the early days of Holmes and Watson's friendship, right from the beginning, so everything you know has not yet formed," Gatiss said. "Sherlock's attitude to women and to crime is still forming, so it's much more 'plastic'.
"The only heresy [about the show] is that it's modern day, but after that it's one of the most faithful versions there's ever been, because [co-creator] Steven [Moffat] and I just love it. Sherlock Holmes had become all about the hansom cabs and the fog, rather than about the friendship of this unlikely couple, but ours is very much inspired by the Basil Rathbone version."
Filming on Sherlock was recently delayed due to the London riots, with Gatiss tweeting: "This is a new one on me. Scene incomplete owing to approaching looters. Unbelievable times."
Sherlock returns in early 2012.