"If any beast were an exception to the laws of space or time, it would be cats" Agnes tells us, although there isn't actually anything mystical about about the homeless cats she cares for despite the latest rumors. Sadly Agnes is surrounded by unenlightened barbarians who perceive cats as vermin so she's having no luck finding a new store front for the shelter after the current one is badly damaged in a magical duel. The only place willing to rent to her must be haunted or something because the last two tenants both left suddenly and without saying anything to anyone. It's not long before she suspects that someone is running an illegal artifact business out of her basement, but it never occurs to her that her mysterious landlord is Havelock himself, the mage who created a spell intended to destroy the world. 

This is a cozy fantasy with a fairly predictable warm fuzzy ending. Shortly after Agnes gets the cats settled into their new home they are threatened by Havelock's evil sister who demands he hand over a legendary tome. Havelock is just the sort of disorganized genius who might have acquired a grimoire disguised as something else and not realized it. Since this magical feud threatens her cats, the very organized Agnes sets out to find it. Along the way she manages to adopt out a few cats and someone starts a rumor that they are magical cats and now everyone wants one or two. Truly, the fantasy of all cat shelter volunteers.