The Octameron is a very loose adaptation of Giovanni Boccaccio's c. 1353 novel, The Decameron, from which is takes its frame story, and The Book of Job, which inspires its thematic resonances and character struggles. The Octameron updates both to the Italian Renaissance: having left Florence to escape the encroaching plague, a group of young men and women amuse themselves by designating one to tell a story each day, using the others as ad-hoc actors. Fiametta, our protagonist, soon realises that the stories her fellow guests are telling are allegorical, giving insight to the complex web of intrigue that spans the group, and that one of them has brought the plague into their refuge. As the disease - and plague-induced paranoia - spreads throughout the group, Fiametta makes it her mission to discover how both infection and intrigue interweave, and if her own sins and guilt over the death of her husband, play a role in what appears to be divine retribution.
The Octameron takes heavily from the themes of loss, theodicy and theomachy explored in The Book of Job, as well as the writings of Reformation-era Christian-deterministic thinkers such as Jean Calvin and Jacobus Arminius. As in Job, what appears as divine punishment is exacted on a group of (at least superficially) virtuous people. Each in turn proposes some kind of theological response to the spreading plague: Fiametta's inner guilt over the death of her husband (and her role in it) prompts her to try to find a causative chain that exempts her sinfulness; Filostrato argues that the host, Dioneo's, role in inviting "heretics, heathens and harlots" into their midst has damned them all; and Dioneo's implicit response, attempting to manage the situation, is an implicit denial of God's absolute agency. Each viewpoint is refuted by the events of the story and in the end, Fiametta comes to accept Pampinea's - and Job's - point of view, that God's will is inscrutable, and that it thus falls to us to live our lives in Grace and recognition of His moral and spiritual power.