Part of a collection called Tales of the Executioners about the vampires in the elite "police force".
It's 1755. With The Guild in it's infancy, there are only so many Executioners, so when a report of mass killings rolls in at Christmas time, Byrn is sent to sort it out. He'd better do something special to appease his wife.
This is the Expanded Edition from Tales of the Executioners, Volume One.