This Article is about the hidden complexity of the textual exception to the Thirteenth Amendment. The amendment mandates that there shall be no slavery “except as a punishment for crime.” At first glance, the exception seems insignificant: The drafters sought to free the slaves, but did not want to curtail the power of state governments to sentence criminals to imprisonment or hard labor. Some courts, however, have interpreted the punishment clause more broadly, holding that prisoners are categorically exempt from the Thirteenth Amendment’s protections. Are these courts correct? The question is not merely academic. The extensive documentation of sexual slavery in American prisons makes resolving the scope of the punishment exception critical. This Article argues that despite the explicit wording of the punishment clause, prisoners retain Thirteenth Amendment rights while in prison. Drawing on multiple approaches to constitutional interpretation, this Article concludes that the Thirteenth Amendment protects prisoners against sexual slavery.