In 1999, dismembered body parts are found scattered across coal factories in Heilongjiang Province, and the victim is identified as Liang Zhijun from an ID card recovered at one crime scene. Recently divorced detective Zhang Zili is assigned to unravel the case, tracing leads to Liu Fayin, a coal truck driver. The ensuing pursuit leads the police to a beauty salon where the operation spirals out of control: several officers and suspects die, and Zhang himself is shot, effectively stalling the investigation.
Five years pass, and Zhang has quit the force, sinking into alcoholism. On a stakeout, he encounters his former partner and learns that two more killings have taken place since the first, with both victims found wearing ice skates and connected to Liang’s widow, Wu Zhizhen, a dry-cleaning worker. Driven by a stubborn sense of justice, Zhang enters Wu’s shop and hands over his clothes, while Rong Rong, the dry-cleaner’s owner, reveals that Wu once damaged an expensive leather coat—the coat owner pursued compensation for a week and then vanished. Wu, aware of Zhang’s surveillance, begs him to back off, but he keeps tailing her, drawn by the mystery and the suspicious quiet in her life.
During another stakeout, Zhang’s bike is tampered with, and Rong Rong’s true behavior comes into focus: she is sexually coercing Wu. Zhang treats Wu’s injuries and clears unruly customers from the shop, all while inviting her on an ice-skating date that she accepts. At the ice rink, Wu veers into a remote area, and Zhang follows, knocking her down and kissing her in a moment that blurs the line between protection and possession. An undercover officer, Captain Wang, notices a truck tailing the couple and confronts the driver, who wears ice skates around his neck and is quickly cut down, a brutal hint of the danger surrounding Wu and Zhang.
Zhang spots a registration plate that Wang had noted and boards a bus, only to see the skate-slung driver shadowing him again. He lures the driver into a crowded nightclub, forcing a halt to the chase. The next day, Zhang tracks the driver to his job as an ice-delivery man, using that to conceal the remains of the first murder victim in blocks of ice and then witnessing the driver drop them onto a coal train from an overhead bridge. He follows the driver to the ice rink and asks the service desk to page “Liang Zhijun”; the driver bolts when the name is announced. Wu is brought in for questioning and confesses to Zhang that Liang had faked his own death to cover the original killing and has since been targeting anyone who gets close to her. Using Wu as bait, Liang makes a fatal appearance, and the police gun him down.
Forensics officers seek ashes from the first victim, but Wu claims she scattered them in the river. Zhang, recalling Wu’s actions five years earlier, confronts Rong Rong again and pushes her to reveal the coat Wu damaged, which leads him to the nightclub Daylight Fireworks. The coat belonged to Rong Rong’s husband, who disappeared with another woman in 1999; she had reported it missing, only to be told he was truly gone. Zhang invites Wu to an amusement-park date, and on the ferris wheel, he points out the flashing Daylight Fireworks sign. He goads Wu, they share a kiss, and their escalating closeness pushes the case to a head.
Wu is arrested the next day and reveals the deeper truth: she couldn’t pay back the coat’s owner and was blackmailed into a sexual relationship. Ultimately, she killed the coat owner, and Liang disposed of Wu’s involvement by concealing his own remains with Wu’s complicity. Zhang watches as Wu is driven away, then heads to a dance hall where he experiences a breakdown, dancing wildly in a raw, unfiltered moment. The police later bring Wu back to her old apartment to gather evidence, and as they depart, a drunk man—implied to be Zhang—sets off fireworks in broad daylight. Wu recognizes him, and she is taken away, leaving the ending ambiguous and drenched in unresolved tension.
