The domed city of Atlantis is attacked by The Brain, who uses sonic brain waves. Aquaman and Aqualad go to investigate and intercept a missile attack with the help of their fish friends. However, after the sonic brain waves are activated, Aquaman no longer has control over the fish, giving The Brain the perfect opportunity to attack Aquaman.
Aqualad finds a city built by a super scientific race. The race turns out to be The Octomen. Aqualad and Tusky are kidnapped by them to lure Aquaman into a trap and find out how he communicates with the sea creatures. While saving Aqualad, Aquaman is captured and forced to reveal how he uses his powers. This gives him an opportunity to call his undersea friends for help. At this moment the trap, an electric octo-giant, is unleashed. Aquaman and Aqualad are forced to find a way of destroying the creature.
Tremors and quakes are causing havoc in the sea. Aqualad is in the area and Aquaman goes to investigate. Turns out that diamond drills controlled by the Molemen, a race of mutants, are causing the problems. Aquaman is captured by the Molemen while Aqualad goes to warn Atlantis and learns of an invasion plan. Can Aquaman save himself and Atlantis?
Mera and her walrus companion Tusky discover a beautiful flower growing out of some silver sand. The flower kidnaps Mera to a water world beneath the regular ocean. Tusky gets Aquaman and Aqualad and they discover that Mera has been kidnapped by the evil Slath. Can they save mera before it's too late?