What occurs behind prison walls is murky. What occurs inside a “prison within a prison,” as many describe extreme isolation, is murkier still. The NYCLU conducted an intensive year-long investigation to shed light on the use and consequences of extreme isolation in New York prisons. Our study involved communication with more than 100 people who have spent time in extreme isolation. We spoke to prisoners’ family members and corrections staff. We analyzed thousands of pages of official records. And we found that New York’s use of extreme isolation is arbitrary, inhumane and unsafe.