Contractor's Note is a written note found in Dishonored.
It's getting harder to find healthy workers who are willing to lay down conduit in the Flooded District. So what we're going to do is pick out any strong-looking males who show signs of the sickness, and offer them work in exchange for us to look the other way. They get these floodlights hooked up, then you do what you want with them.
It can be found in the Flooded District during the mission of the same name.