Solomon Grundy tells the Legion of Doom about the monolith which brought him back from the dead, and which he claims is the source of all evil. He sets the Hall of Doom to dig down beneath the swamp and beyond until it reaches the center of the Earth. Grundy, Cheetah, the Riddler and Gorilla Grodd travel on foot through the molten lava world until they reach the monolith; but it is guarded by a lava monster. The Legion of Doom can't fight the creature, but the SuperFriends can. Using a holographic mirage, they seem to shrink the United Nations building. Then the Riddler leads Superman, Hawkman and Black Vulcan to the center of the Earth, where they find what seems to be the U.N. building. Superman defeats the lava monster and rescues the building, but it's only an illusion. It's really the monolith, and Superman has been tricked into obtaining it for the Legion of Doom. The Legion uses the power source to create worldwide chaos.
—J. Spurlin