Necroscope III: The Source (Necroscope #3)

The series starts to explore the origins of the Wamphyri manifestation on Earth. Years after Harry's son left, Harry has left E-Branch and has spent years searching the world for them. The new head of E-Branch, Darcy Clarke, recruits him in a case of a British spy (Micheal Jazz Simmons) who similarly disappeared, while investigating a Russian base.