The mark of Cain rather than the tradition of St. Anthony is what animates the Irish Catholic gangster in State of Grace. Terry (Sean Penn) is an undercover cop who returns to his old neighborhood of New York's Hell's Kitchen to bring down the Irish street gang he left behind years ago. Although the Catholic tradition of their childhood is available to these wayward souls, they serve the gods of lawlessness betrayal, and violence. The Irish gang headed by Frankie Flannery (Ed Harris), after watching their neighborhood succumb to gentrification, have joined forces with the Italian Mafia. Only trouble is that Jackie (Gary Oldman), Frankie's out of control brother, refuses to get with the new program. He enjoys beating up people, torching buildings, and letting the Italians know that he's not their lackey. Terry's feelings get in the way of his mission when he falls in love with Kathleen Flannery (Robin Wright), a stubborn woman who has unsuccessfully tried to distance herself from her bloodthirsty brothers and their dirty deeds.

For the late screenplay writer, Dennis McIntyre, and director Phil Joanou, these characters all bear the mark of Cain. An old man, who knows them well, tells Terry, "They're black snakes, they'll all turn on anybody." The emotional dynamite in the performances by the outstanding cast lift State of Grace a notch above the traditional gangser movie.