As a young officer, David McDonald got a baptism of fire in Mountjoy. In 1989 it was a chaotic, pungent and overcrowded place, and the approach to keeping order was primitive. Returning to his hometown two years later, he entered Portlaoise Prison, which was then the most secure prison in Europe. McDonald was amazed to discover the power of these subversives within the prison. McDonald's work in a specialist security unit trying to stop this trafficking sometimes brought him into conflict with his bosses. He also questioned aspects of an often brutal and under-resourced system. Ultimately, concerns about poor handling of key issues led to him becoming a whistle-blower. In Unlocked, McDonald brilliantly describes the boredom, the constant tension and flashpoints of extreme violence, and the moments of comedy, tragedy and surprising humanity that are part and parcel of working in prisons.