Superman has left Earth and taken residence on the planet of New Krypton alongside 100,000 Kryptonians newly-freed from the Bottle City of Kandor. Chaos erupts on New Krypton when one of their leaders, General Zod, is shot! When the assassin seeks asylum on Earth, Superman and Supergirl race to locate him and prevent further hostilities between our world and New Krypton. But will their peacekeeping actions be seen as treason to the New Kryptonians? Is this the first step to a war of the worlds?