This French WW2 poster was made to remind workers to return from their work in Germany.
The Service du Travail Obligatoire (STO) was a forced-labour scheme initiated by Germany to deploy French workers, especially within the engineering and construction sectors, into German war production.
The scheme was a classic example of the human resource extraction associated with servicing the military-industrial economy of total war. The administration of the STO was entirely French staffed and their message was based on an appeal to patriotism, coercion and false-promises. Some French military prisoners-of-war were returned in exchange for workers.
I found an academic paper about the propaganda posters of Vichy France by Fabiola Loko
And a French radio broadcast about the story, here
The poster is unsigned, but quite well designed.