With the Riddler holding onto an atomic bomb, Green Arrow attempts to get the mayor to evacuate the city unsuccessfully. When Green Arrow does get the word out to evacuate, however, the bridge out of town is destroyed, trapping everyone inside.
While Riddler is holed up in a stadium holding the city ransom, his employer summons demonic protectors of the city to abolish all crime. The result of which is an EMP wave knocking out all electronics and an army of firey demons who kill those who break the law. To top things off, the incantation has an added side effect that cuts the city off from the rest of the world with a forcefield.