Oceanographer Dan Davidson summons Aquaman to Alaska after discovering that a chemical is killing the fish; a saboteur is setting off explosives at factories; Ocean Master arrives in Atlantis.
A scuba clad saboteur emerges from the frigid ocean depths, plants and detonates explosives in a factory, before escaping back into the sea. In deep waters, off the coast of Alaska, Aquaman and Aqualad arrive for their meeting with one Professor Davidson, a leading Oceanographer. En route, they are attacked by a "school" of fish. The fish are frenzied, and fail to respond to Aquaman's telepathic commands. The pair receive unexpected aid from a deep sea diver. Said diver turns out to be amateur undersea explorer, Phil Darson. On vacation in Alaska, Darson has been investigating the cause of the strange fish madness, a malady that, ultimately, leads to death. As it turns out, the problem regarding the fish is also why Professor Davidson sent for Aquaman. He suspects that waste chemicals from one of the nearby factories is the cause, but all his inquiries have, thus far, been rebuffed. Especially since the previous night's sabotage, which destroyed one of the factories. The professor is in the process of showing Aquaman and Aqualad to their quarters, when the night is rocked by another explosion. The saboteur has struck at the Leland Factory. Aquaman spies the saboteur racing across the ice. He pursues the man into the sea, only to run headlong into a missile. As Aquaman's unconscious body settles to the sea floor, the saboteur makes good his escape.
Aqualad fishes Aquaman's limp form from the icy Alaskan waters. Fully recovered the next morning, Aquaman leads his young ally back into the sea, where the pair begin their own investigation of the suspect factories. A press conference, held at the Leland Factory, finds the company president denying that any acts of sabotage have taken place, blaming the explosions on accidents. Mr. Leland is well aware of the truth of the matter. An investigation into his factories would reveal that chemical waste is being dumped into the sea. A fact he can ill afford to have brought to light. Meanwhile, outside the great dome of Atlantis, the Ocean Master stands under a white flag. Queen Mera, against the advice of her chief advisor, Vulko, leaves the city to meet with the Ocean Master. The villain, however, refuses to speak to Mera. Ocean Master demands to see Aquaman. Back in Alaska, Aquaman and Aqualad compare notes regarding the day's investigation. A clear link between the saboteur and the polluting factories is drawn. Of note to Aquaman is Leland's denial of sabotage, in the day's paper. Since Aquaman knows the truth, he resolves to continue his investigation at the Leland Factory, that night. Aqualad is left behind to keep a watchful eye on Professor Davidson, as a degree of suspicion has fallen on him.
En route to the Leland Factory, Aquaman spies the saboteur returning to the scene of the crime. At that same moment, Professor Davidson has a breakthrough in his own investigation. The saboteur gains easy access to the Leland Factory, only to find Mr. Leland waiting for him. It's a trap. Mr. Leland gets off several gunshots before the saboteur can disarm him. Just as the saboteur is about to kill Leland, Aquaman intervenes. The two battle for several moments. Then, the saboteur hurls an incendiary explosive at the floor. The room is immediately engulfed in flames. Aquaman struggles to reach the saboteur, only to be pistol whipped from behind by Leland. Leaving Aquaman to perish in the conflagration, Leland pursues the saboteur out of the factory. Aquaman is brought back to his senses by the sound of gunfire. With the room consumed in flames, and obscured by smoke, Aquaman is hard pressed to find the egress to escape. Another gunshot rings out. Aquaman follows the sound to freedom. Stepping out into the Alaskan night, Aquaman spies Leland and the saboteur struggling at the edge of a cliff, overlooking the sea. Both plummet to their death. The saboteur is revealed to be Phil Darson. With his dying breath, he tells Aquaman that he could not stand idly by, while Leland polluted the seas. Professor Davidson's findings unequivocally link Leland's factories with the chemicals that are killing the fish. The new owners swear they will abide by E.P.A. pollution regulations. The case closed, Aquaman and Aqualad return to Atlantis.