Called to attend a birth in Little Italy, Sarah finds an anxious family: Young Nainsi Ruocco's baby is being born too early. But when he proves to be a fat, lusty lad, their concern turns to fury - the child was obviously conceived before the girl and her husband had even met. Mama Ruocco, already suspicious of her Irish daughter-in-law, is ready to throw her and the infant into the street, until Sarah intervenes to stop her.
The next morning, Sarah returns to check on the new mother, and finds Nainsi dead in her bed. The family insists that the death was from complications of childbirth. Sarah thinks not. Neither does Nainsi's mother, who spreads the story that the girl was murdered by the Ruoccos - a story that inflames tensions between the Italian and Irish immigrants.
Police Commissioner Roosevelt wants Detective Sergeant Frank Malloy to find out the truth before a full-scale street war develops. But the Ruoccos, related to the leader of the notorious Black Hand, aren't about to turn against blood - and certainly not to an Irish cop. Malloy realizes that once again, he is going to need Sarah's help to unravel the secrets of this troubled family, bring a killer to justice, and restore order to the volatile community.