There was a hand in the darkness, and it held a knife.
The knife had a handle of polished black bone, and a blade finer and sharper than any razor. If it sliced you, you might not even know you had been cut, not immediately.
The knife had done almost everything it was brought to that house to do, and both the blade and the handle were wet.
The Graveyard Book by Neil Gaiman Copyright 2008