Grace Hanadarko is an alcoholic, chain-smoking, self-hating Oklahoma City police detective on a self-destructive downward spiral. Grace is carrying on an affair with her married detective partner, Ham, and occasionally looks after her 12-year-old nephew Clay, who's mother was killed in the 1995 Oklahoma City bombing. Grace also happens to be an atheist having renounced God following the 1995 bombing, but gets along with most of her co-workers including forensic specialist Rhetta, a deeply religious family woman, but is estranged from the rest of her family including her reverend older brother. But one night, Grace experiences a spiritual awakening upon encountering an enigmatic angel, named Earl, who saves her life in a horrific car crash for a chance to redeem her sinful lifestyle. Grace and her team center on the mysterious disappearance of a 10-year-old girl who may have been a serial kidnapper's latest victim, while Grace also learns that a death-row prison inmate, named Leon Cooley, also has a spiritual connection to Earl.