Wow. An incredible journey that takes the main character Frank from self-destruction to redemption. Frank, is an 18 year old, in an occupied country during WWII. He lives with his mother in a whorehouse and spends his time with thuggish losers. He's angry and without direction and so starts on a course that leads to his inevitable demise. He carelessly commits crimes and throws around money and seems to want to get caught.
He finally is caught and is brought to a school being used as a prison. There is where we truly see Frank's transformation. When he lived on the outside, Frank liked to think he knew himself. He was hard by choice, neither happy nor unhappy. Yet to the reader it's clear he's a lost soul. Frank has a lot of time for reflection while in prison. It's not like he repents or anything. It's more like we see glimpses of a better Frank.
Being in prison seems to bring Frank peace. It's like he's a child needing his parents to set some limits on him. It's heartbreaking, his life is a true tragedy. Brilliantly done by Simenon.