HMP Grendon hosts the UK’s only prison-based therapeutic community, inhabited by around 200 residents, almost all convicted of crimes against the person, and about half of whom have killed. This is an inside account of the work, and the theory behind the work, carried out at a prison which not only exemplifies the best in prison philosophy, but also a pioneering approach to the treatment of psychopaths. Previously the Director of Therapies at Grendon, Mark Morris provides a unique insight into the work of this experimental prison regime. He tracks its history from the 1950s, and describes how its approaches have evolved over the decades. He explores Grendon’s status as a provider of a psychological therapy, and positions its treatment process as a therapeutic community, explaining why this approach is so appropriate and effective for helping prisoners with personality disorders, and how the prison environment can help in the rehabilitation of offenders.