Be Warned is a written note found in Dishonored.
Transcript
I found one of our brothers attempting to put a package in the post boxes for the others to find. I believe it to be the evidence of your sister’s involvement in witchcraft you spoke to me about. I attempted to stop him, but he insisted that I would burn for her crimes if I was attempting to cover her deeds. You should warn her. See if the two of you can flee the city before they reach her.
Your friend and brother.
Location
It can be found in one of the mail compartments in the bunkhouse in the Back Yard during the mission High Overseer Campbell.
Trivia
- If Corvo Attano visits the walled-off section of the Back Yard, he will witness Overseer Berthold trying to save his sister from being abducted by two of his fellows. Corvo can intervene to save the pair, granting him a special action.