Sweet 16 or the coveted 18th birthday are milestone moments in a young girl’s life, but the only age Lillian Clemens is dreading of turning is 21. That would mean she's officially old enough to accept the title of Huntsman, an elite fighter born and raised to battle against the supernatural creatures that roam this earth. The only barrier between the human race and the monstrous demons scattered abroad, feasting on the unsuspecting innocents, unable to protect themselves. The night of her first mission, plans go awry and her own Huntsman partner is killed. Shouldering the blame herself, Lillian doesn't refute the rumors that it was her fault Nikolas is dead. The first lesson Huntsmen are taught is to keep your head in the game and not hesitate. But she'd failed. She'd broken the cardinal rule. Two months later, Lillian's planned the perfect mission, to attack and eliminate the creature that took Nikolas away from her. He was the first person that hadn't judged her based on her gender. Since the creation of the Huntsmen organization, only men have been appointed to the prestigious position. But with her father, Oliver, being the Huntsmen Leader, she was born into a role that she couldn't escape. Lillian hasn’t spent a day where wishing she was a man didn't cross her mind. Life would be so much easier. But then it wouldn't be hers. With the mission a success, but not approved by her father, Lillian is punished and given the ultimatum to either train and succeed to become a Leviathan, or die trying. Leviathan's were more ruthless and cunning than Huntsmen, or at least that's what Lillian had always been led to believe. Leviathan's were the soldiers sent in when a mission was deemed too dangerous for a Huntsman. They were the cleanup crew, so to speak. In her quest to assume the title of Leviathan, Lillian must fight for her life against dangerous creatures, but she must also learn that not everyone in this world is as cruel and maniacal as her father and the Councilman who wishes her dead. Opening herself up to the right people, and laying her trust and her heart in their hands, might be the only thing that'll keep her alive.