In his address to Congress in September 2015, Pope Francis surprised many when he included Dorothy Day and Thomas Merton along with Abraham Lincoln and Martin Luther King, Jr, as examples of four “great Americans” he wished to extol. While perhaps better known than Merton, adding Day to the pantheon of great figures in American history was certainly significant. Indeed, since her death in 1980, there has been a steadily growing recognition of the importance of Dorothy Day along with a steadily growing body of scholarship on her. All of which has only been bolstered by the renewed move to have Day canonized. Unfortunately, absent from all this study and promotion of Day and her causes has been much attention on Fr. John Hugo and “the retreat” that exerted such a profound effect on her in the 1940s, bringing about her “second conversion.” There are very real reasons why these important theological sources have been overlooked or even ignored, reasons largely rooted in the context of early twentieth-century American Catholicism. Called to be Saints offers a theological and historical analysis of the role that Hugo and the retreat play in understanding Day and the radical Christianity she put forth—a notion of the Christian life that remains relevant today.