Rather than repeat points others have already made, I'll just give my take on the characters.
Hal: A gravedigger who just wants to be left alone, his visitor though won't leave alone Hal and insists on him coming away with him, I have no idea what sort of pay off is going to come at the end but I assume supernatural action in a 19th century setting.
The dog: Unloved, wants to be fed/loved, will most likely be killed by Hal in the morning and (personally) I'd love for him to become a faithful companion by the end of the story.
Dogs have lots of myths associated with the dead and so could be a source of material. Also if the character is on his own a lot, having the dog along might be useful for character development as treating the dog better could be a way of showing us Hal's recovery from his trauma.
The visitor: Spectral presence, wants Hal for something he probably won't enjoy, I assume that he will be the guide into the story and world.