On October 17 and 18, 1961, during a non-violent demonstration against the imposed curfew, dozens of Algerians were murdered in Paris by police officers acting on orders from their superiors. For forty years, this crime has been concealed; yet these events, the deadliest on French soil since the Second World War, resemble, in some respects, the darkest hours of the collaboration. Why has this history been hidden? Under what conditions, and in the name of what reasons, did officials of a democratic state conceal the scale and gravity of such events?