In Hong Kong, Dr. Gao Jing is introduced to photographer and diver Dave Chen Guo Dong. They fall in love and Guo Dong invites Gao Jing to travel to Taiwan to visit an ancient submarine city, where he intends to propose. During the dive, Guo Dong vanishes, and Gao Jing is unable to recall what happened underwater. Her investigations open her eyes to something far more than she ever expected.