The Greek philosopher Plato twice mentioned the civilization of Atlantis in his work "Dialogues" in 360 BC—"On an indistinguishable night, Atlantis sank into the deep sea." 　　 In 1914, at the Washington City Museum, the young protagonist Milo is a linguist who firmly believes in the legend of Atlantis. Milo aspires to become a great explorer like his grandfather. When he fails to secure funding from the museum, a peculiar friend of his late grandfather suddenly appears, offering Milo the financial support to investigate the truth of Atlantis's existence. 　　 Milo leads a team of experts, forming the most elite expedition, and sets off into the deep sea in search of the city of Atlantis. To their astonishment, the people of Atlantis still live in an underground world. In the kingdom of Atlantis, Milo and the expedition meet the 20,000-year-old king and the 8,500-year-old Princess Kida, who are deeply concerned about the future of Atlantis's civilization. The princess hopes the expedition can help her kingdom regain its vitality. Unexpectedly, the entire expedition team, except for Milo, harbors ulterior motives—they are all driven by greed for wealth. 　　 The expedition plans to kidnap the princess, and Princess Kida is the source of life for Atlantis. Now, Milo must rely on his own strength, with the help of the Atlantean people, to rescue the princess.