S. Gagliano & Son has been a barber shop fixture in South Philly for decades. Frankie and Michael Gagliano's Italian immigrant father--Luigi to his customers, Papa to his sons--presides over the store, enlisting his children as soon as they're big enough to wield a broom. On their mother's deathbed, eight-year-old Frankie swears that he and his little brother will always take care of each other, a vow he endeavors to keep through their father's violent outbursts and the string of wives who try to take their mother's place.

After their father's death, Frankie takes over the shop, transforming it to fit in with the gentrifying neighborhood. Michael becomes a successful prosecutor with a rising political career, still close to his big brother despite the differences between them. Then comes an unthinkable, impulsive act that will force Michael to choose between risking his comfortable life and keeping a sacred oath--made before he knew how powerful a promise can be.