Using many different medieval texts, Schmitt examines medieval religious culture and the significance of the widespread belief in ghosts, asking who returned, to whom, from where, in what form, and why. Through this vivid study, we can see the ways in which the dead and the living related to each other. Schmitt focuses on everyday ghosts - recently departed ordinary people who were a part of the complex social world of the living.

Schmitt argues that beliefs and the imaginary depend above all on the structures and functioning of society and culture, and he shows how the Christian culture of the Middle Ages enlarged the notion of ghosts and created many opportunities for the dead to appear. Schmitt also points out that the church happily proliferated ghost stories as a way to promote the liturgy of the dead, to develop pious sentiments among parishioners, and to solicit alms on behalf of a relative or friend's salvation.