From the back of the book:
Spookshow dealt with those ghosts who could take on mortal form again and who had become literal spooks, going to work as intelligence agents.
This first supplement expands the Spookshow into more unorthodox areas. There are other ghosts out there, ones that can't ordinarily participate as spooks but who would love the chance to interact and to be useful again. Housekeepers, for example, have become a major asset. There are also mortal allies, Professionals and Specialists of all sorts, who can help spies when they're in a jam. Learn more about these ghosts and mortals, how they fit in, and how to play them as characters. Sometimes, even a spook's abilities just aren't enough. Sometimes, what's required is a little bit... more.