When Passion Lies — J.K. Beck

Tiberius is a vampire dedicated to protecting his kind -- and the secrets of the shadow world. Now, as his quest to become head of the Alliance draws within reach, a shattering new threat puts him to the ultimate test. It's a nightmare of grim proportions: a dark plot to bring about the mass extermination of human and shadow alike. And it forces Tiberius to turn to the woman he loved and lost, the lover he still desires but doesn't trust.

Caris was Tiberius's mate for centuries -- until a fateful mission changed her forever. Her tortured secrets drove her into the arms of his rival, but desperation has brought her back. As a horrifying new weapon of mass destruction is about to be unleashed, Tiberius and Caris harness the power of their immortal and passionate love. But will it be enough to battle devastating odds and a ruthless enemy with the ambition to destroy them all?