It’s everywhere, of every size and every color, on the walls of buildings, along railway tracks, on subway cars and even inside tunnels that seem inaccessible. Graffiti is taking over the cities. Some regard it as aggression, others as a form of artistic expression. But who are the graffiti artists? At night, they scale buildings, sneak into subway tunnels. Secretly, they’re taking over the city. You never see them; they hide! For several months, they agreed to let our cameras follow them. An investigation into a new urban guerilla war, a journey into the heart of a strange tribe.