The Emperor of Atlantis has begun his invasion of Earth. When the erstwhile supervillain Dr. Regulus loses his entire robot assembly factory to a sudden attack of Atlantean Exiles, the Atlantean Isles prepare for war. The leaders of the Lost Isles, James Chase, Tane Casak, and Jayesh Khatri prepare their islands for the battle they've known was coming for so long.

As the Exiles emerge from portals and swarm the islands with a fearsome mechanized army, HeroTube fights back alongside the Atlantean Defense Force. James Chase fights to rescue his sister from the Exiles, who have captured her and are using her earth powers against them. Tane Casak deploys the Mercurion against the giant mecha of the Exiles, and victory seems assured … until the Emperor brings the death island Tyrona out of its prison dimension. Now the heroes of the Lost Isles and HeroTube alike must fight for their lives against the Emperor of Atlantis and his superweapons.

Because after three hundred years, Atlantis alone will not satisfy the Emperor's lust for conquest.