Answer:

The central irony in The Plague lies in Camus' treatment of "freedom." The citizens of Oran become prisoners of the plague when their city falls under total quarantine, but it is questionable whether they were really "free" before the plague. Their lives were strictly regimented by an unconscious enslavement to their habits. Moreover, it is questionable whether they were really alive. It is only when they are separated by quarantine from their friends, lovers and families that they most intensively love them. Before, they simply took their loved ones for granted.