Set in the 4th century, the film follows the story of Sebastian, a Christian and former Roman soldier who is exiled to a remote desert outpost after refusing to renounce his faith. Stripped of his rank and status, he finds himself among a group of disgruntled soldiers led by the cruel and sadistic Captain Severus. The oppressive and harsh environment of the outpost forms a backdrop to the intense personal dynamics and escalating tensions among the men. While Severus becomes increasingly obsessed with Sebastian, the latter maintains an unwavering dedication to his beliefs, resulting in profound clashes with the other soldiers who struggle between duty, desire, and their personal demons.

Sebastian's peaceful resistance and spiritual conviction provoke various reactions from his fellow exiles, leading to growing hostility and envy. His chastity is particularly provocative to Severus, who becomes fixated on breaking Sebastian both physically and spiritually. The outpost turns into a crucible where the soldiers' suppressed emotions and violent tendencies bubble to the surface, heightening the sense of peril for Sebastian. Despite facing relentless persecution and brutal punishment, Sebastian’s steadfast faith provides him a sense of inner peace, even as the tension among the soldiers reaches a boiling point. The story is an exploration of human cruelty, devotion, and the conflict between flesh and spirit within the microcosm of a hostile, isolated environment.