Dr. Gao Jing, a psychiatrist, becomes entangled in a web of memory, mystery, and submerged secrets when she joins a group of environmentalists for a daring seabed project. The mission aims to bury carbon dioxide beneath the ocean floor, but it is interrupted by a chance encounter with Guo Dong, the brother of Gao Jing’s patient Xiao Kai. A photograph taken during the dive leads to an unexpected romance, thrusting Gao Jing into a relationship that soon pulls her away from ordinary life and into a haunting overlap of past and present.
Guo Dong takes Gao Jing on a journey to the Ryukyu Islands, guiding her to the fabled Yonaguni, an ancient underwater city that sits like a secret between worlds and time. There, he hides a ring with intentions to propose, a gesture meant to affirm their growing bond. Yet tragedy strikes in a way that feels almost inexplicable: Guo Dong is suddenly beheaded in a mysterious accident that leaves Gao Jing and those around her searching for meaning in a scene that should feel closed but instead opens up a deeper, more troubling mystery.
Meanwhile, Xiao Kai is overwhelmed by doubt at her brother’s funeral. The body lacks a head, and the fingerprints have worn away, leaving her convinced that the remains can’t be her brother. She grows convinced that he might still be alive, and she becomes determined to uncover the truth. Her investigation leads her to a shipwreck site where she teams up with Haiya Amu, a friend of Guo Dong, and the pair unearth a white-haired severed head that she insists must be her brother’s. This discovery intensifies the sense that the story is not simply a tragedy about a missing person but a portal into something more cryptic and unsettling.
Back with Gao Jing, memory and perception begin to fray. She loses the clarity of her own recollections and agrees to undergo hypnotism therapy under the supervision of her boss, Dr. Tang, plus a regimen of drugs designed to unlock what she cannot recall. The side effects are immediate and disorienting: a heightened sensitivity to bright lights and loud noises that throws her daily life into sharp relief and makes the world feel dangerously bright. She notices a similar sensitivity in her patient, Simon, who confesses that he has seen something like a dripping wet ghost—Guo Dong—haunting him. Gao Jing leans into the possibility that the ghosts are more than figments, and she asks Simon to help her contact Guo Dong, even as she warns that she might be pursued by a specter of guilt and fear.
As the story unfolds, Gao Jing returns home to a new riddle: Xiao Kai speaks with a different accent, and Gao Jing suspects that Xiao Kai may be channeling the ghost of a young woman from Hualien, Su Zhenjing. This intensifies the sense that the living and the dead are intermingling in the same space. Xiao Kai asks Gao Jing to open a canister containing the recovered head, but Simon warns against it. The danger becomes immediate when Xiao Kai accidentally injures Simon by running him over, sending him to the hospital as the tension between the living and the dead grows more dangerous.
Haiya Amu is sent to verify the origin of the head, but he returns home to find a knife in his back and is killed. Gao Jing reacts with fear and resolve, throwing the severed head from the balcony before being attacked by Xiao Kai; the police intervene to prevent further violence. In the tense aftermath, Gao Jing takes more of the hypnotic drugs to reach out to Guo Dong, and Guo Dong’s ghost appears to offer protection, saving her when she nearly falls down the stairs. The spirit explains that his oxygen tank was damaged by currents, and Gao Jing invites the ghost to stay with her in the present, where memory and spirit seem to share the same air.
Gao Jing then returns Haiya Amu’s head to his father and has a final, quiet exchange with Guo Dong. The story shifts to Gao Jing waking up in a hospital, where she has remained since her boyfriend’s disappearance, with no clear memory of what happened. Xiao Kai recounts how Guo Dong disappeared after saving Gao Jing from nitrogen narcosis, and a camcorder video seems to confirm a shocking twist: Gao Jing stabbed Guo Dong during her narcosis. This revelation reframes the earlier events as the collision of memory, guilt, and spectral presence rather than a straightforward disappearance.
Driven by this new truth, Xiao Kai brings Gao Jing home and cares for her as she confronts the haunted past. Gao Jing experiences a dream where Guo Dong asks her to travel to Feng Lai to find him, a summons that prompts her to seek out the missing pieces of their shared story. She discovers a taped recording in which the stabbing would appear to have been erased, leaving only unanswered questions and the need to pursue the truth further. Her journey carries her to Feng Lai, where she finds Guo Dong’s cabin and a trove of lost photographs that offer glimpses of a life they shared and the secrets that bound them.
On a sunlit beach, Gao Jing finally discovers the ring Guo Dong had meant to give her, a tangible symbol of the promise they never fully realized. Rather than a conventional happy ending, she walks into the ocean, drawn by the pull of Yonaguni and the memory of what they shared. In the final moments, the ghosts of Gao Jing and Guo Dong are shown swimming together around the submerged city, suggesting that their connection transcends the boundaries of memory and life, lingering in the underwater world where the past continues to breathe.
The story remains a meditation on memory’s fragility, the lure of legends beneath the sea, and how love can persist even as it dissolves into the currents of time. It invites viewers to weigh what is seen against what is believed, what is remembered against what is lost, and what it means to be haunted by a truth that refuses to stay buried.
