Batman visits Aquaman during an investigation into some unusual seismic activity. There he discovers that Aquaman's brother Orm is working with Black Manta to conquer Atlantis.

The evil Morgaine Le Fey has taken over Camelot and Etrigan and turned everyone to stone! To thwart her plans, Merlin transports Batman and Green Arrow back in time to retrieve Excalibur, battle dragons and return King Arthur to the throne.