At first you’re thinking it’s just Moriarty’s book cipher but if you watch this one a couple times you understand what they did. The best thing about Holmes stories is how a clever screenwriter can mold them into different genres while protecting the canon. Take the first one, it’s classic buddy cop – detective – CSI stuff but then you get into the political motivations, chemical weapons, industrial revolution, secret societies, and turn of the century hysteria. It’s a lot of fun but doesn’t quite take it as far as the 2nd. A Game of Shadows watches more like a spy thriller with espionage, counterespionage, warmongering, conspiracy to start international conflicts, agents and double agents, honey pots, exploitation of underground rebel groups to promote state-to-state conflict, assassination, arms factories, body doubles, etc.
So yes, there’s a cipher, oohh a book cipher! Ciphers are actually a welcome portion of several Holmes stories. It’s the covert action, human intel side of this Sherlock movie that really makes it a welcome addition to any cryptographer/intelligence fan’s movie list.