Sirius Trouble - The Thomas Hunter Files: Realm Travelers, #1

A new Thomas Hunter adventure. The world has changed. The Rise of the Sirius star is showering Earth in a surfeit of occult radiation, giving birth to a host of new phenomena, not the least of which is a novel strain of vampire. The Old-World Therians are in danger of extinction and a new species of bloodsucker is on the rise, and they're not interested in merely sipping blood like a fine wine. It was business-almost-as-usual with Hunter exterminating the regular occult creepy crawlies, and the occasional wayward vamp that just had to get in his way, when a certain blondie showed up on his doorstep.
Morgan was sent by Hunter's old friend, Dax, and Hunter wasn't exactly thrilled because in addition to manifesting as Rat Therian, his new guest had one hell of a secret that could threaten a whole lot more than basic sanity. In fact, it just might bring the house down on all of their heads because Morgan had gotten herself in trouble with the vamps known as the Dark Ones who were not only poised to take over the local vampire scene, but the whole damn world.
From there it didn't take more than a few rounds loaded into the semi-auto, and his finding of a certain alchemical trinket that might be more important than the Holy Grail, for Hunter to realize they were all in Sirius trouble.