The Tower's Alchemist (The Gray Tower Trilogy, #1‪)‬

A jaded spy reluctantly agrees to postpone retirement and extract a warlock from Nazi-occupied France. But when her cover is blown, she’s pitted against a deadly vampire who seeks to devour her.

It’s an alternative World War II, where magic is not only real but is key to winning the war. Isabella George, a battle-weary alchemist and spy for British intelligence, wants nothing more than to retire and find love—but fate has other plans for her. She parachutes into Paris, bent on destroying an alchemical weapon known as the Plague and nabbing Veit Heilwig, the warlock who created it.

It seems simple enough, but there's a catch. Someone within her own spy organization betrays her and exposes her identity, putting her life in danger and setting Marc, a Cruenti vampire, hot on her trail. Isabella is shaken by the fact that Marc wants to steal her powers, but she’s determined to regain her footing and complete her mission. She still holds out hope that she can retire to a normal life, but Marc won’t make it easy for her. He sends his minions, both human and inhuman, to hunt her down.

Adding to the complexity of the situation, Isabella navigates the romantic attention of two men, both of whom bring out the best in her. She must decide if they will be a help or hindrance to her, in her deadliest mission yet.

Reading Order of The Gray Tower Trilogy
* The Tower's Alchemist (Book 1)
* Dark Rift (Book 2)
* Circadian Circle (Book 3)