Arnaud Mustier is a lawyer and a philosopher, who can put everyone at a stand with his words. But everything begins to fall apart. He finds himself diagnosed with a teenage syndrome. This is one of the rare disorders and affects adult men, which makes them againget through the crisis of being a sixteen-year-old teenager. Arnaud discovers a world of teenagers, surprising everyone around with his behaviour. The first to see him in his new role was his own teenaged brother.