Mera finds life as Queen of Atlantis increasingly more lonely, as Aquaman is constantly away patrolling the seven seas. Aqualad stays behind to keep her company, however, the boy's impetuousness proves to be too trying for Mera to handle, without Aquaman. As her displeasure grows, she begins acting out against her Atlantean subjects. While Aquaman is away, a strange fish arrives in Atlantis, carrying Mera's old hand mirror, left behind in Dimension Aqua. Once the mirror is imparted to Mera, the image of Dimension Aqua's greatest scientist, Xeron, appears within the looking glass. He has repaired, to some degree, the gateway device for transit between Dimension Aqua and Aquaman's world. Professor Xeron can send people, or things, from Dimension Aqua to Mera, though he cannot, as yet, bring them back again. Mera immediately sends for her old "pet", a horrific sea creature she calls "Choggar". Mera is overjoyed to see the beast, climbing aboard it's back to ride it around Atlantis. The Atlanteans, however, are not as fond of the path of destruction the creature leaves in it's wake. Soon, a group of Mera's old friends cross over from Dimension Aqua, to take up residence in Atlantis. They quickly wear out their welcome with their rambunctious behavior and disrespectful ways. As the Atlantean's umbrage towards Mera's friends increases, so too does their contempt for the new Queen. Meanwhile, on the surface, a man known as T.T. Taggert is making plans to add Aquaman, and the Atlanteans, to his "Aquacade", a water themed amusement park. To that end, he has allied himself with Nikkor, one of Mera's friends. Taggert will make sure Aquaman never returns to Atlantis, if Nikkor will deliver the Atlanteans to Taggert's "Aquacade". Nikkor orders his companions, from Dimension Aqua, to round up the Atlanteans, for transport to the surface. Aqualad bears witness to the capture of the Atlanteans, and immediately swims off in search of Aquaman.
Aqualad finds Aquaman freeing Kraka, a giant squid, from a fishing trap. Aquaman is stunned to hear that Nikkor has usurped the Atlantean throne, as well as Mera's seeming complicity in selling the Atlanteans into bondage. Aquaman and Aqualad immediately swim back to Atlantis, but they are ambushed by Taggert's men. The two heroes take cover within a giant scallop, but when Aquaman orders it to re-open and release them, he discovers that the scallop is made of steel. Taggert has trapped them. Taggert places a 24 hour guard on Aquaman, with orders to kill the sea king, if the Atlanteans do not perform in Taggert's "Aquacade". Soon enough, Taggert is making huge profits, due to the popularity of his latest attractions. Under duress, Aquaman, Aqualad, and the Atlanteans put on the greatest water show in history. Below the waves, in Atlantis, it is revealed that Nikkor has been regularly drugging Mera, since his arrival, to bring her in line with his scheme to become King of Atlantis. Back at the "Aquacade", Aquaman is rehearsing a new show, commanding octopi and squid, penned in adjacent pools to the Atlantens, to project water from their ink sacs into the air. In effect, Aquaman has created mollusk fountains. Their true purpose, though, is not to entertain Taggert's audiences, but to increase the water level of the Atlantean's tank until it overflows, spilling over the lock gate, into the sea. Aquaman instructs Aqualad, and the Atlanteans, to swim for the ocean, while he holds off Taggert's men, buying them the time to escape. Believing the whole affair to be just another part of the show, the audience breaks into thunderous applause, even as Aquaman is overwhelmed by Taggert's forces.
Aware that Aquaman cannot survive out of water for more than one hour, Taggert places him in a glass diving bell, in clear view of a clock. Taggert will release Aquaman only if he agrees to order the Atlanteans to return to the "Aquacade". Aqualad and the Atlanteans forcibly take back Atlantis. Nikkor and Queen Mera are placed on trial for treason. On the surface, the clock winds down on Aquaman. Taggert is shocked that the sea king did not break, sacrificing his life for the sake of the Atlanteans. Under cover of darkness, Taggert return's Aquaman's limp body to the sea. Aquaman, however, is only feigning death. While all eyes were on him in the diving bell, Aquaman commanded a passing sea gull to move the clock's hands forward. Mera and Nikkor are found guilty, and sentenced to live out their lives in the Dungeon Depths. Aqualad races back to the surface, encountering Aquaman, already en route to Atlantis. Aqualad reveals Mera's fate to Aquaman. Then the two race off to stop the Atlanteans from carrying out the sentence. Arriving too late, Aquaman, to the shock of the Atlanteans, hurls himself down into the Dungeon Depths. The inescapably powerful ocean current drags the sea king down, miles deeper, until he finally reaches the bottom. Mera is overjoyed to be reunited with her husband. Nikkor states that the drugs he had given to Mera, to make her compliant with his wishes, have clearly worn off. In a murderous rage, Aquaman attacks Nikkor. Their struggle though is interrupted by the emergence of a nightmarish, subterranean, aquatic horror. One that does not obey Aquaman's commands. Forced to work together to stay alive, Aquaman and Nikkor attack the creature, stabbing at it with broken pieces of stalagmites. Mera spies her hand mirror floating down to them. Again Professor Xeron's face appears in the glass. He has completed repairs on the gateway between their two worlds. They can escape back into Dimension Aqua. The news comes too late, though, as the creature has already grabbed Aquaman, it's grip too strong for the sea king to break free. Nikkor calls to Mera to leave with him through the portal, but Mera refuses. She will stay with Aquaman until the end. In a sudden change of heart, Nikkor re-attacks the creature, stabbing at it repeatedly until it releases Aquaman. Nikkor sacrifices himself, remaining behind to divert the creature, while Aquaman and Mera escape to Dimension Aqua. Back in Atlantis, Aquaman explains to the Atlanteans that Mera had not been in her right mind, due to Nikkir's manipulations. All is forgiven.