Germany locks up roughly 58,000 people, and more than half reoffend after release, numbers that push this DW documentary to ask whether prison actually works. Journalist Frank Seibert has himself locked in a cell for a few hours to feel what isolation and lost control do to a person, then takes the question to the people who run the system. Lawyer and former prison governor Thomas Galli argues that 90 percent of inmates could be safely paroled, and points to the cost, about 200 euros per prisoner per day, more than 10 million euros daily nationwide, as money better spent on therapy and social work. Prison officer René Müller defends incarceration as necessary for safety and deterrence. Criminologist Kristin Drenkhahn discusses how a prison's social climate shapes rehabilitation, former prisoner Thomas describes what years inside did to him after a violent crime, and neuroscientist Simone Kühn presents early brain-imaging research into whether monotonous confinement shrinks the regions prisoners need to function afterward.