Knights of the Blood — Scott MacMillan

THE HOLY LAND, 1291
In the never-ending crusade against their Turk enemies, knights of the Order of the Sword, in the fury of battle, commit a blasphemy that taints their noble lineage and leaves them consumed by an insatiable hunger for blood....

THE ARDENNES, 1944
Nazi soldiers besiege the castle of the Order of the Sword to gain the secrets of immortality from the centuries-old crusaders -- by spilling and drinking their blood to be reborn as vampires....

Los ANGELES, Now
Ace detective John Drummond of the LAPD is investigating the case of a body bearing Nazi tattoos, found drained of blood. Its a crime that echoes the unsolved murder of a half dozen men decades ago. Drummond thinks he's on the trail of a human monster -- a vicious serial killer who has eluded the law for decades. But the truth, he will soon discover, is much, much worse....