 Solomon Grundy informs the Legion of a  single source of all-evil power  which he believes is buried in the center of the Earth. The Hall of Doom soon drills down through the Earth in pursuit of this monolithic evil power. Unfortunately for the Legion it is guarded by a giant lava monster. They devise a scheme to fool the Superfriends into getting the power source for them. Superman, Hawkman and Black Vulcan soon have fallen into the Legion s trap and must fight for their lives in the subterranean labyrinth while the Legion wreaks havoc with the power source above ground.