Hector Cole has been working as a freelance paranormal investigator long enough to have seen most of what the supernatural considers unusual. Edmund Strange, curator of the Museum of Mysticism and Monstrosity, contacts Cole with a case that exhausted every conventional approach: a visitor vanished under circumstances that rational investigation cannot explain, and Strange's reputation is at risk. Cole arrives at the museum and immediately registers the distinct sensation of being observed by something that should not be watching him.