Have you ever wondered what would happen if you went looking for vampires? What if you secretly believed they existed? Dylan decides to go on a vacation of a lifetime in order to find herself. She begins in Romania, contemplating the existence of vampires and quickly realizes that she was wrong. Once she ends up in Florence, however, she is confronted with an immortal, Nico. She must be marked if she wants to live because she learned the truth of vampires. Nico catches her and her heart by surprise. The Mortal One is a whirlwind romance amidst vampire politics. Dylan must be marked for her safety, yet she is trying to be claimed by another vampire, thus making her time in Florence very complicated for her. She tests the bounds of her relationship with a vampire and tries to create a life for herself as the mortal one. The main setting of the book is Florence, Italy, where Dylan is in love with the history of the city.