Superman and Aquaman must battle Dolphin-Men, amoebic mutants with telekinetic powers and a wish to destroy the human race.

A mysterious high pitched buzzing sound, along with a dazzling underwater rainbow, leads Aquaman to an Oceanographic laboratory. The lab is in ruins. A single page from a scientific journal fills Aquaman with a sense of foreboding. As Aquaman explores the island, he encounters a band of weird dolphin-like men. Their awkward gait causes the King of The Seven Seas to laugh uproariously. Aquaman's laughter clearly enrages the creatures, who lash out with their telepathic powers. Aquaman falls to the ground, unconscious. In Metropolis, television news reporter, Clark Kent, encounters a desperate man, searching for Superman. Suddenly the man bolts. As Kent pursues the man through the streets, the crowds of bystanders go blind in their wake. Kent, too, finds his vision impaired. The blurry image of his quarry stops, then seems to split into two.

Both figures continue to race away. With the crowd blind, Kent switches into his Superman costume. His own vision, though, is impaired enough that he accidentally side swipes a passing car, while giving chase to the two figures. Superman keeps the car from crashing. As soon as Superman's vision clears, he continues his pursuit, catching up with his quarry, as they approach a nearby island. On the island, Superman spies the unconscious form of Aquaman. Superman immediately gets Aquaman into the ocean, where the Sea King quickly revives. As the two men return to the island, they are approached by one of the strange dolphin-like men. It is this one, which came to Metropolis in search of Superman.

As a child, the dolphin-like man was abandoned by it's parents.The creature was found, frantically splashing about on the surface of the sea, by a pair of oceanographers. These men raised the creature in their laboratory. It reached adolescence in a matter of months, and quickly learned to speak English. It also developed various psychic powers. Though graceful in the water, the creature was extremely awkward in it's movements on land, eliciting the laughter of men. Horribly lonesome, the creature discovered that it could asexually reproduce, and split a twin off from it's body. The twin, while sharing all of it's brother's powers, had none of it's brother's love of humanity. It, too, could asexually reproduce, and soon, the creatures' numbers had expanded. They destroyed the oceanographic research center, and made plans to melt the polar ice caps. With humanity consumed by the rising seas, the dolphin creatures would rule the world. Superman, Aquaman, and the dolphin-man go to confront the dolphin creatures.

Suddenly, Superman sees an enormous sonic monster hovering over the sea. The Man of Steel breaks off his assault on the dolphin creatures to confront the new threat. Aquaman, and the dolphin man, fight on valiantly, but soon enough, the dolphin man is felled. Aquaman summons a school of fish to provide him with cover, to momentarily flee. A whale breaks the dolphin creatures' battle formation. Out of the whale's mouth comes Aquaman. With the element of surprise on his side, Aquaman begins to beat back the horde of dolphin creatures. With their focus shifting more and more on Aquaman, the illusion of the sonic monster they placed in Superman's mind begins to fade. As soon as Superman realizes his foe is merely an illusion, he rejoins Aquaman beneath the sea. The dolphin man, too, recovers, and rejoins the fight. With the dolphin creatures defeated, Superman carries them all off world, to an uninhabited planet they can call their own.