What is the black man's signature?
In "The Devil and Tom Walker," Tom meets a man in the swamp who claims to be the devil. The man offers him the treasure of a famous pirate in exchange for his soul. Tom is surprisingly receptive to this exchange, but wants some kind of confirmation that what the man is saying is true. The devil puts his thumb on Tom's forehead and calls it his signature. When Tom returns home and looks in the mirror he finds that he has a black thumbprint that seems to be burned into his forehead and which he cannot remove no matter what he tries. This signature, along with the death of well known member of the community which the devil had predicted, convinces Tom that the man is in fact the devil and that what he has been saying is true.