To save his brother's soul, Casimir Warlin is forced to exchange his own to a demon, forever bound to serve her in secret. In a cruel twist of fate, he learns he was born to be a venator, a hunter of extraordinary capabilities who exists to defeat demons.

Casimir is prepared to accept a life of servitude to protect his last living family member, until a dangerous opportunity presents itself to him and his master--an invitation to a prestigious venator academy. As he enrolls and departs for his new mission, he risks his secret and the souls of his new friends. It's the ultimate betrayal, but it's part of the deal.