In my story I would have a completely independent and elusive guild of assassins. They would not be sanctioned by either a king, wealthy merchant, nobleman or by the church. Because of that, if it turns out that the guild actually exists, members would be hunted down in an attempt to shut down the organization because it would be a threat to those in power.

Assume that this is a medieval world without magic and that the guild has managed to remain completely hidden. What is missing in my story so far: How does the guild accept assignments without getting noticed or found out?

I have a few options, but I'm not sure if they're feasible and what other options there are:

• The guild uses traveling story tellers: medieval style tv/radio commercials.
• Inn-keepers or socialites who know the protocol required to contact the guild.

Either way these intermediates would otherwise have a normal occupation, would be compensated for their efforts and have no direct contact with the guild so they couldn't betray an individual.