Assumption is the story of a slave named Nathan living in a racially hostile environment in antebellum and post-Civil War Louisiana. Assumption Parish was the kind of place where slaves were whipped frequently, where disease and rustic living were the normal course of life, where the swamp, with all its savage foreboding, loomed nearby. It was a place, Nathan discovered, that traded in men's spirits, breaking them little by little for purposes that were difficult for him to comprehend. Like many slaves of his time, Nathan is raised without biological parents. His surrogate mother, Abbie, longs for the day when slavery ended. But she is too conservative in nature, too aware of her powerlessness, to do anything to force change. Nathan's surrogate fathers, on the other hand, are only too willing to rebel against the plantation system. Nefs, in fact, covertly plots revolt. He hopes Nathan will join him in this crusade. But even after being brutally whipped for a petty, accidental infraction of the plantation's unspoken code of conduct, Nathan does not fight back but instead opts to run from the plantation. This illusion of leaving the harshest of the Old South's conditions was fomented by Nathan's other surrogate father, Pinder Beauregard, who dreamed Nathan would become a New Orleans musician as Pinder once had been. Eventually, the plantation's slaves revolted and Nathan escaped, though not before witnessing Pinder death in battle. Nathan wanders the swamp where he discovers freedom is not what he'd expected. Every institution, from the military to religion to marriage, is closed off to him. Nathan falls into a deep fever, like the kind that killed his parents. He is returned to the plantation where he grew up, recovering to find the plantation has changed little since he's been away. The biggest shock is the fate of Nefs, who has been rendered into a catatonic, bootlicking, house servant. Nathan sees in Nefs his future self, a strange alien puppet with barely a mind of his own. He decides his musical life can wait until he can begin a campaign to topple the post-Civil War society.