The Mettray Penal Colony was a private reformatory without walls, established in France in 1840 for the rehabilitation of young male delinquents. Foucault linked its opening to the most significant change in the modern status of prisons and now, at last, Stephen Toth takes us behind the gates to show how the institution legitimized France's repression of criminal youth and added a unique layer to the nation's carceral system. Drawing on insights from sociology, criminology, critical theory, and social history, Stephen Toth dissects Mettray's social anatomy, exploring inmates' experiences. More than 17,000 young men passed through the reformatory before its closure, and Toth situates their struggles within changing conceptions of childhood and adolescence in modern France. Mettray demonstrates that the colony was an ill-conceived project marked by internal contradictions. Its social order was one of subjection and subversion, as officials struggled for order and inmates struggled for autonomy. Toth's formidable archival work exposes the nature of the relationships between, and among, prisoners and administrators. He explores the daily grind of existence: living conditions, discipline, labor, sex, and violence. Thus, he gives voice to the incarcerated, not simply to the incarcerators, whose ideas and agendas tend to dominate the historical record. Mettray is, above all else, a deeply personal illumination of life inside France's most venerated carceral institution.