Allure: A Watcher Series Prequel - The Watcher Series, #0.5

There's no turning back when you're on the run. As America tries to forget the horrors of the Great War by embracing jazz, flappers, and the speakeasy, the Watchers remain vigilant by protecting the innocent and maintaining order among the Immortals-including a powerful line of Seers who are all but extinct. But the real horror is just beginning. When George Yates is ordered to escort the beautiful Rosemond Le Clair to safety, he finds himself in the middle of an ancient feud that demands her blood.
Without the Watchers' help, he must struggle to protect the last remaining daughter of the Le Clair family from these dark powers, even as he defies fate itself.