Nearly Christmas - Filthy Henry, #5

Mortals magically murdered generally is enough to get Filthy Henry, Ireland's first and foremost fairy detective, involved in the case. But when those murders happen on Halloween there is even more reason for him to investigate what is going on. As the walls between Realms weaken, allowing spirits to roam the land, Filthy Henry and Shelly are in a race against time to ensure All Hallows Eve goes off without a hitch.
Otherwise dead mortals are going to be the least of Ireland's problems...