Game warden Seeley Houk's mutilated body is found floating in the Mahoning River and rookie Pinkerton detective Dominick Prugitore intends to apprehend the culprits who murdered his friend. But first he must infiltrate an Italian community perched on the bluffs above the Mahoning River between New Castle and Youngstown, Ohio. This ramshackle collection of immigrant shantytowns provides cheap labor for quarries mining limestone for the steel mills in nearby Pittsburgh; the newspapers call it "bloody Hillsville." Dominick's first order of business is to gain the trust of and join a secret, cutthroat association called The Black Hand, the dreaded Mafia of his Italian homeland. This is a world of secret codes, duels, vendettas, assassins, bizarre initiation rights, unbridled law enforcement, prejudice, bigotry, and the near slavery of immigrant laborers.
The Black Hand is an organization held together by the "Omerta," an oath of silence. Breaking the Omerta is the key to solving Houk's murder, but to disobey the Omerta carries a sentence of death, and Dominick must take the vow knowing he is duty bound to violate it.