When Darkness Hungers (The Shadow Keepers #5)

FBI agent Alexis Martin knows that vampires exist—because one of them killed her sister. Assigned to investigate a series of bizarre homicides in Los Angeles, Alexis believes the murders are the work of rogue vampires—perhaps even the monster responsible for her sister’s death. Now she finally has a chance for retribution. Even better, Alexis receives unexpected help from a sexy stranger as hungry for rogue blood as she is.
 
Serge is a centuries-old bad boy who stays off the grid—keeping his secrets, his hunger, and his heart safe from exposure. A new breed of vampire that feeds off other shadowers, Serge finds sweet torture in Alexis’s arms. Loving her is a chance to be free from the hiding, the loneliness, the secrecy. But the truth about what he is, and what he’s done, may banish him to the dark confines of his own private hell—and destroy the beginnings of their love.