I thought that was the plan all along, to have the mice eventually be lured out by playing the violin. :) Maybe that could be a way to ... convince a character to leave a room.
Difficulty is quite the task but there are options. I mean, there's already one in the build - calling Mycroft. Another one could be a short highlight of interactive areas. It will be interesting to see how the observation mechanic will work. Will Hol... the player's character be able to "see" details before talking to NPCs? Will you have to go back and forth to see the portrait of the NPCs & pin-point details that unlock new dialogue options?
I think the solution for this one is not elementary Watson...
Oh, and, will Sh... the player's character have any pets?