Ghost Moon by Rebecca York

On a vital mission from a parallel universe, Quinn meets werewolf Caleb Marshall, who was killed 75 years ago by his cousin and has stayed on earth to avenge his death. Everything changes when Caleb acquires the body of a murder victim. But can he and his cousins work together to foil a diabolical plot aimed at the heart of the U.S. government? Can his love for Quinn survive the terrible irony that fate had dealt him?