Mastering Fear analyzes horror as play and examines what functions horror has and why it is adaptive and beneficial for audiences. It takes a biocultural approach, and focusing on emotions, gender, and play, it argues we play with fiction horror. In horror we engage not only with the negative emotions of fear and disgust, but with a wide range of emotions, both positive and negative. The book lays out a new theory of horror and analyzes female protagonists in contemporary horror from child to teen, adult, middle age, and old age. Since the turn of the millennium, we have seen a new generation of female protagonists in horror. There are feisty teens in The Vampire Diaries (2009-2017), troubled mothers in The Babadook (2014), and struggling women in the New French extremity with Martyrs (2008) and Inside (2007). At the fuzzy edges of the genre are dramas like Pan's Labyrinth (2006) and Black Swan (2010), and middle-age women are now protagonists with Carol in The Walking Dead (2010-) and Jessica Lange's characters in American Horror Story (2011-). Horror is not just for men, but also for women, and not just for the young, but for audiences of all ages.