In the summer of 1974 a heatwave blankets Boston and Mary Pat Fennessey is trying to stay one step ahead of the bill collectors. Mary Pat has lived her entire life in the housing projects of "Southie," the Irish American enclave that stubbornly adheres to old tradition and stands proudly apart. One night Mary Pat's teenage daughter Jules stays out late and doesn't come home. That same evening, a young Black man is found dead, struck by a subway train under mysterious circumstances. The two events seem unconnected. But Mary Pat, propelled by a desperate search for her missing daughter, begins turning over stones best left untouched, asking questions that bother Marty Butler, chieftain of the Irish mob, and the men who work for him, men who don't take kindly to any threat to their business.