Patrolling the Atlantic Ocean, Aquaman and Aqualad are alerted to danger in Atlantis, by a signaling lantern fish. Racing to the ancestral home of his mother's people, Aquaman encounters the Atlantean, Pomoxis, just outside the great domed city. It is Pomoxis who has sent word to Aquaman, via the lantern fish, that Atlantis is threatened. A series of underwater explosions have been occurring with alarming frequency, not far from Atlantis. Pomoxis fears that the detonations will grow nearer still, potentially reaching Atlantis, utterly destroying it. Aquaman and Pomoxis race to investigate the source of the explosions, leaving Aqualad behind, to inform the Atlanteans that help has arrived. Aquaman and Pomoxis discover large amounts of gas emanating from fissures in the ocean floor. Moving closer, the pair are caught in another explosion. En route from Atlantis to rendezvous with Aquaman, Aqualad sees the flash, but is too far away to determine if Aquaman or Pomoxis have come to any harm. Upon reaching the site of the explosion, Aqualad finds Aquaman staggered, but uninjured. Aquaman informs Aqualad, and later the Atlanteans , that Pomoxis died in the explosion, buried under tons of rock and debris. Aquaman also assures the Atlanteans that the explosions are merely volcanic eruptions, the worst of which having passed. Aquaman and Aqualad depart Atlantis, resuming their oceanic patrol. No sooner do they break the surface, then they run across a sinking cargo ship. Aqualad ushers the crew onto the back of a sperm whale, while Aquaman tries to save the cargo. In short order, Aquaman is unable to salvage the ship's cargo before the ship explodes & sinks to the bottom of the sea. When Aqualad questions Aquaman as to why he did not summon the fish to aid him, Aquaman snaps at his young charge. Ordering Aqualad to get the ship's crew to shore, Aquaman, angrily, swims away. Aqualad worries that the earlier explosion may have affected Aquaman's mind. The truth is far more sinister, for "Aquaman" is really Pomoxis, wearing an impossibly perfect Aquaman disguise. During those few moments that Pomoxis and Aquaman were caught up in the underwater explosion, a rift in time opened. Pomoxis shoved Aquaman through it, changed into his Aquaman costume, & took Aquaman's place, the better to exploit the trust the world has for the hero, making it easier for Pomoxis to maraud the seas. The real Aquaman was rendered unconscious by the powerful forces that drew him through time. He awakens to see a Persian galley bearing down on him
The Persians immediately attack Aquaman, believing him to be a Greek warrior. Aquaman easily outdistances the Persian warship, making his way to a nearby island. There he is met by a Greek army. The Greeks were witness to the Persians attack on Aquaman, and welcome him among them. The army was to cross over to the mainland to bolster the ranks of the Greek forces, led by Militiades, against the Persian invaders. Their ships were sunk, though, by a recent earthquake, leaving them marooned. Aquaman summons a pod of whales to carry the Greek army, and their arms, to the mainland. They have arrived to late to aid Militiades' forces, as the Persian fleet has already arrived. Inspired by the engraved image on a Greek warrior's shield, Aquaman rides out on dolphinback to meet the Persian fleet, declaring himself to be Poseidon, the Greek God of the Sea. The Persians scoff at this boast, attacking Aquaman with spears and arrows, all of which are plucked from the air by the mouths of fish. Octopi then hurl swordfish at the Persian sailors. Followed by whales battering the Persian galleys to splinters. With the Persians routed, Aquaman returns to the Greeks, who hail him as Poseidon, returned to save his people. Aquaman allows the masquerade to stand, wondering if he will ever see his time again.
In the present, Pomoxis continues his own masquerade as "Aquaman". On his next patrol with Aqualad, he suggests splitting up to cover more ocean between them. Aqualad is put off by the idea of separating the team, but reluctantly complies. Alone at last, Pomoxis quickly closes in on a passing cargo ship. Diving beneath the waves, Pomoxis orders sawfish to cut into the cargo ship's hull, allowing octopi to make off with the bounty. As the ship sinks, the crew escape in life boats. Pomoxis returns to his lair, with plans to convert the looted ship's goods into gold and silver. Soon enough, Pomoxis will be the wealthiest man in Atlantis. Suddenly, Aqualad appears, catching Pomoxis in the Aquaman costume, but with the mask pushed off his face. Pomoxis had ridden off on the wrong porpoise when he parted ways with Aqualad, revealing himself to be an imposter. Aquaman always rides his favorite porpoise, "Porpy". Pomoxis quickly overpowers Aqualad, carrying him to a remote island. It's sole structure an abandoned lighthouse. Bound tight, Aqualad is left to die, drying out in the sun, as his hour-out-of-water time limit expires. At that moment, 2500 years ago, Aquaman spies the same gas, rising to the surface, that preceded the explosion, that hurled him through time. Aquaman dives down into the gas, desperate to find another hole in time, to return him to the present. The ocean floor is violently shaken by an earthquake, which topples an underwater mountain, raining rock and debris down on Aquaman. All seems lost.
Back in 1962, Pomoxis, as "Aquaman", continues his reign of terror on international shipping lanes. Aqualad is seconds away from fatally succumbing to dehydration. Gasping his last breath, he is stunned to suddenly find Aquaman at his side. Freed from his restraints, and returned to the sea, Aqualad is filled with questions. Aquaman details his narrow escape from beneath the crumbling mountain. Another rift in time had, indeed, opened. Aquaman sped through it before he could be completely buried. His favored porpoise, "Porpy', had led him to Aqualad, in the nick of time. Now it was time to confront Pomoxis. Alerted by his early warning signal fish, Pomoxis spies Aquaman and Aquald closing on his lair. Armed with a speargun, Pomoxis steps out to face them. Aquaman summons a school of swordfish to put down Pomoxis, but Pomoxis parries the attack with his own swordfish. Aquaman sends octopi to attack Pomoxis on his right flank, but again Pomoxis has his own octopi, that defend him. Aquaman stampedes giant sea horses at Pomoxis. Pomoxis lassos them with eels. Pomoxis counters Aquaman's catfish with dogfish. Too evenly matched, there seems to be no way to break the stalemate. Aquaman, though, has one last strategy left to try. Diving into a bed of kelp, Aquaman maneuvers around to take Pomoxis from the rear. Pomoxis has seen him, though, sending torpedo fish into the kelp bed to pummel Aquaman. Downed, cling fish drag Aquaman's unconscious body over to Pomoxis, who levels his speargun at Aquaman's head. As the cling fish bring Aquaman closer, Pomoxis is startled to see that it is actually a large sea turtle, wearing his "Aquaman" costume, and not the hero himself. Before Pomoxis can react, Aquaman is upon him. In the struggle, Pomoxis drops the speargun, which the sea turtle spirits away. Aquaman defeats Pomoxis, turning him over to the Atlantean authorities. Aquaman reassures the Atlanteans that the explosions they so feared were simple volcanic eruptions, and that he had first hand knowledge that they had been going on for a long time. They would not be encroaching upon Atlantis. Aquaman and Aqualad take their leave of Atlantis, with the intent of returning all the ill-gotten goods garnered by Pomoxis.