Bernt Lund harbours a sickness. He is a monster: in the mind of society, in the mind of his two nine-year-old victims' parents, and in the mind of his fellow inmates. Lennart Oscarsson harbours a secret. Yet he is seen as dependable: in the eyes of his family, in the eyes of colleagues, and in the eyes of the prisoners he oversees. These men's weaknesses will soon hand DCI Ewert Grens the most profoundly sickening and impossibly sensitive case of both his career and Stockholm's history. Pen 33 is both an unforgiving collision between a time-hardened policeman and a truly heinous crime, and an unflinching exploration of what people - whether criminals or victims - are capable of when they choose to relinquish self-control.