The secret of the Trench revealed! Where did these cannibalistic sea creatures come from? What fuels their monstrous hunger? Why have they chosen now to invade the surface world? To unravel the mystery of the Trench, Aquaman must seek help from the last person on earth he ever wanted to see again.
In a flashback, Tom stands alone at the pier in sunrise while young Arthur is playing nearby. Shedding a tear, Tom wishes that Atlanna, Arthur's mother, could be here and see how much Arthur has grown. Arthur comes to his father and asks him why does he come to the pier every sunrise, and Tom replies that he wants to be there when his mother returns.
In the present, Aquaman and Mera continue fighting the Trench. Then, the Trench begin to retreat. Aquaman and Mera, wondering where are the Trench going, investigate the cocoon the Trench made. Aquaman opens it, revealing a dog. A wounded Trench appears, but is quickly shot to death. The military tries to take the body for study, but Aquaman and Mera take the body and leave.
Aquaman and Mera go to a house in the coast, where a man named Stephen Shin lives. According to Aquaman, Shin was a friend of his father's who taught him how to use his powers. And then, he tried to kill Aquaman because he would not take him to Atlantis.
Entering the house, Aquaman and Mera ask Shin to perform an autopsy on the Trench, and Shin reluctantly agrees. Shin deduces that the creature is a new type of sea lifeform that lives in the Mid-Atlantic Ridge, out of the Trench. Shin wants to keep the body, beleving it will help restore his credibility, but Aquaman won't let him. Desperate, Shin asks Aquaman where is Atlantis, but Aquaman simply leaves.
As Aquaman and Mera swim to the depths of the ocean to find the creatures's lair, Mera asks what will they do once they find the creatures's victims. Aquaman replies that they don't know what the creatures are yet. Mera believes that if the victims are food, then they must desperate for food and that they must be on the verge of extinction. Aquaman replies that if that's ture, then the creatures are just trying to survive, just like they are.