The devil is perhaps the single-most recurring character in Old English narrative literature, and yet his function in the highly symbolic narrative world of hagiography has never been systematically studied. Certain inconsistencies characteristically accompany the nebulous devil in early medieval narrative accounts - he is simultaneously bound in hell and yet roaming the earth; he is here identified as the chief of demons, and there taken as a collective term for the totality of demons; he is at one point a medical parasite and at another a psychological principle.

Satan Unbound argues that these open-ended registers in the conceptualisation of the devil allowed Anglo-Saxon writers a certain latitude for creative mythography, even within the orthodox tradition. The narrative tensions resulting from the devil's protean character opaquely reflect deep-rooted anxieties in the early medieval understanding of the territorial distribution of the moral cosmos, the contested spiritual provinces of the demonic and the divine. The ubiquitous conflict between saint and demon constitutes an ontological study of the boundaries between the holy and the unholy, rather than a psychological study of temptation and sin.