The history of espionage, even in the Classical or Medieval or Renaissance periods that so frequently inspire elements of fantasy settings, is enormous and deep. It's also probably filled with holes in information, because so many resources were probably destroyed or lost due to their covert nature. So, if you plan to use spies and coded messages in your game, how can you turn those story elements into challenges or hooks for player characters? Below are a few brief thoughts on the form that spies might take, along with notes on how they might be treated, and a few example methods for passing secret information that could be slipped into any game.