Erc Foner's book is less the comprehensive history of the Underground Railroad that its subtitle might suggest than a history of what he terms the "Metropolitan Corridor" -- the network that passed through or near New York City. This is because of the discovery which inspired the book: the "Record of Fugitives" kept by Sydney Howard Gay, an abolitionist journalist who in the 1850s helped assist hundreds of slaves escaping bondage. Yet this important source and the events it chronicles serve as just one part of the book, as Foner goes back further to describe the beginnings of the informal networks that arose in the 1830s to both aid fleeing bondsmen and to prevent the seizure by slave catchers of free blacks off of the streets of New York. Through his description of the people involved and the often dramatic events in which they were involved he illuminates the efforts of a group of Americans who undertook great efforts to make the promise of freedom real for thousands who were denied it by the color of their skin. It's a story that deserves to be told, and it's one that Foner tells well.