Skullduggery by Kathleen Karr
Matthew is only twelve when his parents die and he is left on the streets of New York City to fend for himself. He jumps at any chance of work because it means that he will be able to eat that night. He takes on all kinds of odd jobs trying to keep himself alive when he seee anotice in the paper for a boy to do work in exchange for room and board.
He decides to answer the add and trys to make himself presentable. He goes to the address in the paper and it is here that he encounters the mysterious Dr. ABC. He learns that the Dr. is in the most strange and interesting brance of medicine: phrenology, the science of judging character by interpreting bumps on the skull. It only gets better! He finds out that part of his work will be robbing graves for specimens for the Dr. to study.
They set out on a quest for particular skulls, lurking around graveyards, digging up graves to find what it is they are in search for. The Dr. likes to keep the skulls on the mantle and frequently talks to them as if they are real friends. Matthew is somewhat dubious about this new turn of events but he wants to be able to stay with the Dr. and so consents to help him achieve his goal.
It is while they are searching for these famous skulls that they learn that someone is trying to get rid of the two of them. That is when they encounter the bodysnatcher. He is a fearsome man that they meet up with in the graveyard. He is very large, strong and not so fun to look at.
they manage to get away from the bodysnatcher and press on with their mission.
You have to read the book to find out what happens to Matthew and Dr. ABC before all is
said and done. It's creepy, scary and fun!