For all of you Musophobes out there, I should mention that, despite the title, our story does not feature any rats whatsoever. The Rats in the title instead come from a quote from Charles Dickens' short story "Tom Tiddler's Ground" where a character discusses a filthy man's bedclothes as "heaving and a heaving with the rats under em" . "But", asks our narrator, was it rats? For in another case, he admits that it was not.  There are other things that heave and shiver under the covers of what should be an empty bed, in what should be an empty room...things that are worse than mere rats...much worse.