The villainous Mephisto sends his minions to plant a sleeping pill in the Atlantean oxygen generation plant, which will enable him to easily take over the city. The plan is foiled when Aqualad manages to slip inside the machinery and pull the pellet back out. Mephisto then tries to destroy Atlantis with his ships' weaponry, but Aquaman summons an army of marine life that disable the craft. Leaving the villains for the "Atlantean cleanup crew," the heroes withdraw to let Aqualad sleep off getting too close to the sleeping pellet.