On Christmas Day in 2020, Lin Yu was on a blind date with his third match of the day when he got a call from the police station. At the scene, he found a male victim who had fallen from a building. Beside him lay a cross made of branches. The police immediately sealed off the area, then identified the victim as Gao Yu, a single father with a four-year-old daughter. The death appeared to be a murder. The area was remote, with no surveillance cameras or other clues.
The day after Christmas, the police station suddenly received a strange emergency call. The caller said just one sentence, then hung up. As it happened, a psychology intern, Zhang Sisi, had just joined the station. While everyone was at a loss, Zhang Sisi noticed something odd about the voice and suggested checking emergency call records from the past year. They found that a similar call had come in the previous Christmas, and that such Christmas calls had continued every year since 2015. The police quickly focused on the school Gao Yu had attended in 2015, but as they investigated, they found that things were far more complicated than they had imagined. Yu Wei, the person behind the voice on the phone, had died in 2014. This was an impossible emergency call. Like a "murder from the future," was this the victim's revenge, or was there another killer? In the struggle between crime and justice, who was pulling the strings behind the scenes?
