A navy submarine mysteriously sank in the Mariana Trench. The Justice League sent Cyborg Victor (voiced by Shemar Moore) to investigate, but Victor was attacked by a group of mysterious opponents at the scene of the accident. After that, Superman (voiced by Jerry O'Connell), Diana (voiced by Rosario Dawson), Flash (voiced by Christopher Gorham), Green Lantern (voiced by Nathan Fillion), Batman (voiced by Jason O'Mara), Captain Marvel and other Justice League partners gathered at the headquarters one after another. After a joint investigation, they found that the real culprit behind the scenes was related to ancient Atlantis. Led by the ambitious Prince Orm, this group of deep-sea warriors declared war on humans, and a full-scale war between the two races was imminent. At the critical moment, Arthur (voiced by Matt Lanter), a man who had just suffered the pain of losing his father, became the key to the incident. Taking this as an opportunity, the fate of Arthur and the entire Justice League has changed...