"Steal. Trade. Survive."

That's what Father tells Rose and Lem moments before he dies of the Great Plague.
Orphaned and homeless in London 1665, all Rose and Lem have left are their wits, each other, and three bottles of Thieves Oil — a medicinal blend Father created that can protect people from the sickness.

But then Lem goes missing, and Rose is left to fend for herself. As words of Thieves Oil spread to London's most desperate scavengers, Rose must band together with her fellow street orphans, steal the essentials to survive, and protect herself and her newfound friends against both the Plague and a world filled with dangers.