Eel, an orphan, and his best friend Florrie must help Dr. John Snow prove that cholera is spread through water, and not poisonous air, when an epidemic sweeps across their London neighborhood in 1854.

In March of 1887, Rocco, an eleven-year-old from an Italian village, arrives in New York CIty where he is forced to live in squalor and beg for money as a street musician, but he finds the city's cruelty to children and animals intolerable and sets out to make things better, whatever the cost to himself.