The Boston Police Department was formed by a man who had twice failed in business, ran a bar in the poorest district of Boston, and was charged with two assaults. When Francis Tukey became City Marshal in 1846, he faced off against some of the most notorious criminals of the time. Under Tukey's leadership, the police were known for their coordinated "descents" on gamblers, rumrunners and prostitutes.

This book aims to recount the story of the formation of the Boston Police Department, featuring many of the department's earliest cases and crises. Significant tales include the conflict following the Fugitive Slave Act of 1850, when Tukey and his officers avoided enforcing the law, even helping enslaved people further escape. Also covered are the department's dealings with Irish refugees and the Cholera epidemic of 1849.