Police officers are obliged to give an account of every incident they are involved in. But what happened today will never be logged. Because that's what police solidarity means: what happens in the van stays in the van. Well, not always. Not this time. What really happens behind the walls of a police station? To answer this question, investigative journalist Valentin Gendrot put his life on hold for two years and became the first journalist in history to infiltrate the police undetected. Within three months of training to become an officer, he was given a permit to carry a weapon in public. And although he lived in daily fear of being discovered, in his book Gendrot hides nothing. 'Cops' is a gripping exposé if a world never before seen by outsiders.