Jack Miller, Daniel Gillies, an American lawyer based in Tokyo, is haunted by a childhood nightmare about his younger brother Sean, Ethan Amis, who drowned when their rowing boat capsized while Sean tried to retrieve a baseball cap. The memory lingers as survivor’s guilt, coloring Jack’s sense that his attempt to save Sean was somehow incomplete. In the present, Jack finds himself drawn to Yuri Saito, Yoshino Kimura, the wife of his most valued client, Eiji Saito, Ryo Ishibashi. Despite a deep-seated fear of the sea, Jack agrees to join the couple for a day trip to Tokyo Bay, convinced that Eiji simply needs a quiet moment to work out a difficult legal matter. Yet beneath the cordial surface, tension simmers: Yuri and Jack’s affair is not a secret, and it begins to look as if Eiji senses the betrayal and may have murderous plans of his own.
As the boat sails, Eiji’s mood swings grow more alarming, and Yuri’s trust begins to crack. The voyage reveals a darker history: Eiji had married Yuri after his first wife—Naomi Saito, Miho Ninagawa—vanished under circumstances that never fully made sense. When the ship’s screw stalls, Eiji dives under the boat to clear the blockage, and instead of seaweed, he pulls at hair tangled in the machinery, a clue that something far more sinister is at work. The hair yanks him down, and he is pulled into the depths—dead or alive, no one can be sure. Yet moments later he reappears, drenched and alive, as if the sea itself had brought him back. The situation grows stranger still: no other boats respond within range, and the radio crackles with a voice that isn’t theirs—Sean’s, calling Jack by name—turning the day into a creeping, underwater suspicion that something supernatural is now steering events.
The mood shifts from uneasy to dangerous when Eiji tries to kill Yuri, and Jack and Yuri realize that something has taken hold of Eiji—something not entirely human. Naomi’s vengeful spirit seems to possess him, using his body to punish Yuri for a past grievance. In a brutal confrontation, Eiji overpowers Jack, and the struggle ends with Jack stabbing the possessed man; Eiji falls apart and tumbles overboard. The bathroom of the boat fills with water as Jack wrestles with the severed, floating arm of the fallen man, a grisly reminder of how thin the line between harm and protection can be. Yuri is pulled into a perilous trap, nearly drowning, as Naomi’s grip intensifies.
As Yuri teeters on the edge, she receives a vision that exposes Naomi’s motive: Naomi had attacked Eiji’s first wife to secure her own inheritance, dumping Naomi’s body at the same spot where the current peril unfolds. With the radio ruined and no ordinary means of rescue, Jack must act quickly to keep Yuri safe as Naomi’s influence intensifies. In a chilling sequence, Naomi presses forward, but Sean’s ghost again intervenes, countering Naomi’s ploy and revealing that the apparent threat was a cruel trap meant to drive Jack into harming Yuri. The supernatural pressure eases, and Yuri, battered but resolute, urges Jack to take a decisive leap of faith. They jump overboard, hoping to escape the clutches of Naomi’s vengeance as the boat disappears into the distance.
In the tense chase that follows, Naomi reappears to drag Yuri under once more, but Sean returns to intervene again, pulling Naomi back to the depths where she belongs. The final turn of the tale finds Jack and Yuri surviving the ordeal and choosing a life together, a fragile peace earned through fear and courage. The from-hell memories recede as Jack accepts that Sean never blamed him for his brother’s death, and that his future could finally begin with Yuri by his side.
