Dead Boys Detectives by Ed Brubaker

Featured in Sandman Comics - this collected one storyline. Neil Gaiman created the characters and Ed Brubaker wrote this comic.

The Dead Boy Detectives are Charles Rowland and Edwin Paine, two British schoolboys from different eras who are now ghosts. They take on a case of missing homeless teens who are later discovered shriveled and horribly dead. Since no one is taking this seriously one of the homeless teens find the detectives in their tree house and asks for their help. So in typical young boy fashion they both jump in feet first to the fray of witches, immortality and the occult. Not bad for a couple hours of reading.