On January 1, 1983, during a New Year’s Eve celebration, Ji-hwan, a dedicated high school teacher, proposes to his colleague and girlfriend, Yoon-Jung. Just after the moment of joy, Yoon-Jung notices her purse has been slashed and emptied, prompting [Ji-hwan] to chase the robber. The pursuit devolves into a violent struggle, and Ji-hwan is fatally stabbed, leaving a young couple’s hopeful future abruptly cut short.
Fast forward to New Year’s Eve in 2015, a rookie detective named Gun-woo and his team navigate a crowded celebration as they close in on a suspect. In the heat of the pursuit, Gun-woo witnesses the tension of the moment and wrestles with whether to shoot; he is fatally shot himself, an event that fractures the ordinary flow of time for those who survive. Remarkably, 32 years apart, [Ji-hwan] and [Gun-woo] end up in the same hospital on the same day and time, each surviving near-death experiences and discovering an uncanny link between their lives: they begin to see through each other’s eyes in dreams. At first, the phenomenon feels unbelievable, but it soon yields real clues that bridge their experiences and push them toward a shared mystery.
As the visions deepen, Gun-woo reviews surveillance footage and spots a woman who bears a striking resemblance to Yoon-Jung. He pursues the woman, who turns out to be So-Eun, though she is initially mistaken for a flasher. After a tense exchange, So-Eun is brought to the station, where her identity is confirmed, and Gun-woo’s status as a detective becomes clear to the people around them. The strange connection between the two men nudges them toward collaboration, weaving the personal with the investigative threads of the case.
Meanwhile, the Chief of Police assigns Gun-woo to file reports on cold cases, which leads him to an unsolved murder from the 1980s—one in which Yoon-Jung is the victim. Ji-hwan, guided by the dream-derived knowledge of Yoon-Jung’s fate, vows to guard her on the day she plans to try on her wedding dress. Yet fate intervenes: a city-wide air strike disrupts the plan, and Ji-hwan’s frantic search takes him to a gambling house where a man who seems to be a suspect flees. In a brutal turn, Ji-hwan confronts the man, who inadvertently knocks Yoon-Jung to the floor, and Ji-hwan discovers her dead body in a public restroom.
As the investigation unfolds, the suspected killer turns out to be the father of one of Ji-hwan’s students, but a string of subsequent deaths with similar methods quickly reveals that this figure is not the true culprit. So-Eun, who works at the same school as the couple, becomes an essential ally to Gun-woo, helping him piece together clues that the case spans decades. Yet the danger intensifies when So-Eun herself appears to be killed in the same method as Yoon-Jung and other victims, suggesting the serial killer may still be alive and active. With time running out and the connection between their lives growing stronger, [Gun-woo] and [Ji-hwan] resolve to unravel the mystery together, determined to stop the killer and bring closure to the lives touched by the case.
