The Doctor and Donna arrive at a planet that is one huge library, simply called The Library.  Things are not what they should be however, as there is no one around.  They begin to investigate and are met by a group of space suited people doing the same.  The leader of the new group, named River, happens to know the Doctor pretty well, even though he's never met her.  They Doctor determines that the Library is infected with creatures that live in the shadows called Vashta Nerada.  After the eat Proper Dave, they use his body (or skeleton) to go after the rest.  Meanwhile, a little girl who somehow has a connection to everything, "saves" Donna by snatching her teleportation signal.