In Hong Kong a family moves into a newly bought apartment: May Shu Qi Cheng, her husband Ray Alex Fong Chung-Sun, and their young son Chi-lo Tam Chun-Ho settle into their new home. The fresh walls and quiet corridors feel safe at first, but a sense of unease lingers as May and Chi-lo both catch a glimpse of a hideous creature wandering the building. Ray, trying to be practical, suggests moving out to protect their child; yet with a sizable price already paid, the family decides to stay, hoping the danger will fade.
Their fears intensify when, at a neighbor’s birthday party, Chi-lo is kidnapped. The kidnapper is later revealed to be Chan Yim Hung [Karena Lam Kar-Yan], a deformed, insane woman who has mistaken the boy for her own missing child. After notifying the police, May and Ray launch their own desperate search through the apartment complex. In the parking garage, Ray is stabbed by the woman with a crude blade and is left critically wounded, rushed to the hospital as alarms and panic ripple through the building.
With neighbors reluctant to help, May pushes onward alone. She crawls through the building’s air ducts, narrowly escaping another attack and nearly falling victim to the kidnapper. A dog is brought in to aid the search, its keen nose tracing a scent to a rooftop, but the hunt is brutal: the dog is killed by Chan, though not before it bites off one of Chan’s fingers. May retrieves the severed finger from the dog’s mouth and carries it to a police detective, hoping for a lead.
The fingerprint from Chan’s severed finger identifies her as Chan Yim Hung, a woman who once lived in the same squatter area as May’s family. Years earlier, when the government moved to reclaim the area, a riot erupted and Chan’s husband was killed in an explosion. The squatter zone was cleared, but Chan returned with her son Wing-man [Tam Chun-Ho] to try to reclaim a life there. Wing-man’s death during those turbulent times had shattered Chan, driving her to madness. This backstory, revealed through the investigation, helps May understand the motive behind the kidnapping: a desperate mother clinging to a past that no longer exists.
To draw Chan out, May prints and distributes copies of Chan Yim Hung’s photos through the complex’s air ducts, provoking the woman to strike. Chan bursts into May’s apartment, demanding the return of her son. May tries to explain that her own son Chi-lo had died years earlier, but Chan’s fixation remains unyielding. Chi-lo arrives during the confrontation, and Chan drags him out of the apartment while driving away with May’s child in danger. The chase spirals back into the building’s utility systems, where Chan, haunted by a vision of her dead husband, pleads for the past to return. A reflection in a glass door of an electrical grid shatters the illusion and triggers a blackout that sweeps through the entire complex.
As the blackout grips the complex, May sees a cloth belonging to Chi-lo drift down from the sky, signaling that the rooftop is their only refuge. She fights her way past police investigating the outage and confronts Chan on the rooftop. The two clash as May fights to save Chi-lo, finally stopping Chan from harming her son. In a final, desperate act, Chan leaps to her death with Chi-lo, seeking reunion with a family that can no longer exist in the world they inhabit.
The scene closes with May and Chi-lo embracing, the city below them still in darkness. In the quiet aftermath, Chi-lo’s voice breaks the hush with a haunting question, revealing the depth of his fear and longing:
> Mom, would you abandon me?
May’s steady resolve answers him with quiet warmth and certainty: “Of course not, not even if you abandon me.” The long night of fear ends with a promise of protection and a fragile, renewed bond between mother and child, even as the memory of the storm lingers in the air and the building slowly returns to light.
