The novel takes place in the 11th Century Middle East, where the charismatic leader of a radical Islamic sect, known as the Ismailis, manipulates and controls his followers through a combination of religious indoctrination, drugs, and the promise of paradise. The leader creates a literal paradise within the walls of his fortress, Alamut, in order to convince his followers that they are experiencing the afterlife. The story explores themes of power, manipulation, and the nature of faith.

The book follows Darius Kellner, a half-Persian teenager living in America who struggles with clinical depression and feels disconnected from his heritage. When his family travels to Iran to visit his ailing grandfather, Darius grapples with the complexities of identity, belonging, and friendship. In Iran, he forms a bond with Sohrab, a boy who helps him understand the value of true connection and the importance of embracing his cultural roots. Through this transformative journey, Darius confronts his internal battles and learns to navigate the intricate landscape of family expectations, mental health, and self-acceptance.