The narrative follows the life of Barabbas, the criminal spared from crucifixion in place of Jesus, as he struggles to reconcile his violent nature with the lingering presence of a faith he cannot comprehend. Barabbas navigates a world defined by brutality and the shifting political landscape of the Roman Empire. His objective is to find meaning or relief from the existential weight of his survival, yet he remains perpetually alienated from the believers he encounters. The narrative framework utilizes a third-person limited perspective to observe his internal isolation and his physical encounters with the early Christian movement. He is constantly opposed by his own inability to believe and the harsh, unforgiving realities of his criminal past.

Discussion often centers on the stark, unadorned prose style that Lagerkvist employs to examine the human condition. Readers frequently highlight the effectiveness of the protagonist's internal conflict as he grapples with the shadow of a man he never truly knew. Critics often point to the novel's ability to balance historical atmosphere with deep philosophical inquiry regarding the nature of faith and redemption. The work is widely regarded for its refusal to offer easy answers, instead focusing on the persistent alienation of its central character. Many readers find the depiction of the early Christian community through the eyes of an outsider to be a particularly compelling aspect of the narrative.