After waking up in a morgue, an orphaned teen discovers she now possesses superpowers as the chosen Halo Bearer for a secret sect of demon-hunting nuns.

In response to a global rise in demonic possessions, the Catholic Church reopens exorcism schools to train priests in the Rite of Exorcism. On this spiritual battlefield, an unlikely warrior rises: a young nun, Sister Ann. Thrust onto the spiritual frontline with fellow student Father Dante, Sister Ann finds herself in a battle for the soul of a young girl and soon realizes the Devil has her right where he wants her.

Two doctors find their graveyard shift inundated with townspeople ravaged by sores. Among the wounded is Cherry, a dancer whose leg was ripped from her body. As the invalids quickly become enraged aggressors, Cherry and her ex-boyfriend Wray lead a team of accidental warriors into the night.