Letter from Mr. Weatherby is a written note found in Dishonored 2.
Don't come back to the shop. I'll find a new assistant, one who doesn't feel the need to discuss the political validity of the taxes with the Grand Guard when they come to collect their protection money. By the way, the extra fee they requested will be retained from your last wages.
Bring me back the shop key and make sure I don't ever see your face again.