Philadelphia, 1835. The journey begins.

Kicked out of her third school for fighting, 11-year-old tomboy Rian Krieger gets an unanticipated education in her father's factories. The City of Brotherly Love is a roiling stew of rivalry, prejudice, and change that pits German artisans, Irish immigrants, and the largest population of free Blacks in America against one another.

Steam engines choosh throughout the city. Workers dig ditches for new gas street lights. The fledgling railroad industry hints that change will soon come even faster.

Rian is swept into this racial and economic turmoil by three charismatic mentors. Foreman Jules Freeman, one of the few Black men in Philadelphia placed in charge of whites, introduces Rian to the Underground Railroad.

Rian's Irish cousin Seamus strives to prove himself amidst the hostility of Otto's German workers and launches a new fire brigade with a controversial mission. Next-door neighbor Lucretia Mott finds her voice as a stirring abolitionist.

Rian befriends Olivia Tucker, the daughter of slave owners from Charleston who summer in Philadelphia. Together, they plot to free Olivia's mammy from enslavement. Secrets pile up. Rian finds that she must apply Rule #1 to many parts of her life.