Okay, I think that this is desperation on the brink of madness. Why try to find a way home when you can get someone else to do it for you? Poor cute l'il shadow spirit...
A word of warning - the British postal service is not very good at delivering even properly-addressed letters; I'm not sure how they will react to whatever a Denizen thinks is Art's postal address! It does show how indestructible the little guys are though; a letter's life is not an easy one with all the sorting machines and being stuffed at the bottom of sacks!
