Children of the Night — Mercedes Lackey

The Gypsy boy had asked for Di's help--called on her for magical assistance--and she could not refuse, especially after he was slain practically on her doorstep.

But the vampire Di finds cradling the body isn't the killer--he's the Gypsies' protector, Andre LeBrel, who informs Di that there's more than one monster stalking the streets of New York.

Now it's up to Diana Tregarde, Guardian and practicing witch, to find the killers and destroy them...with a little supernatural assistance from a very friendly, and very sexy, vampire!