In 1993, a serial murder case occurred in Hong Kong. While chasing the suspect, Senior Inspector Yang Guangyao of the Crime Unit accidentally traveled through time and space in an elevator to 2018.

However, during this period, there was no news about Guangyao's wife and daughter, and the previous cases were still unsolved. Thanks to the help of his former boss, Guangyao returned to the police station as an undercover agent and resumed his duties. He met a partner who had a completely different style of handling cases from him.His origins also aroused suspicion.

At this time, a new murder case appeared, and there seemed to be a bigger conspiracy behind the murder case. Many clues reminded Guangyao of the murder case that year. In this adventure, he finally recognized that his partner who was just around the corner turned out to beHis daughter also learned that his wife had been killed after he traveled through time. He vowed to catch the murderer and go back to the past to change everything.

In Mong Kok in 1993, in a no-parking area, the blind sign relied on his status as the boss and refused to move his car, even if he faced penalties for plagiarism.At this time, Yang Guangyao took the initiative to intervene. After understanding the situation, he was ready to assist the police in getting the blind bidder to hand over his car keys.However, the boss of the blind bid suddenly appeared and deliberately threw the key into the sewer in front of the police, intending to walk away.Upon seeing this, Yang Guangyao rushed forward without hesitation, preparing to search him, and suspected that the other party might have taken drugs.Before the other party could refute, he decided to thoroughly investigate the store run by this person and locked the vehicle next to him.Seeing this, the other party had no choice but to compromise.

After handling the parking incident, Yang Guangyao quickly threw himself into the investigation of another murder case.He quickly arrived at the crime scene and met newcomer Liu Weitao.After the two greeted each other, they began to inquire about the details of the case and learned that no murder weapon was found at the scene.After learning that the deceased's name was Deng Rongtian, Yang Guangyao began to observe carefully, trying to find out the cause of death.However, the newcomers couldn't help but gag at the sight of blood all over the floor.Yang Guangyao stopped him in time and calmed his emotions.Later, the police took some suspects away for interrogation, but the suspects did not cooperate and deliberately caused trouble.After dealing with the troublemakers, Yang Guangyao reported the situation to his superiors and believed that this was not a simple indoor robbery.Before leaving, he specifically asked his colleagues to stay calm.

Since then, many serial killings have occurred in Mong Kok.As a police officer, Yang Guangyao rushed to the scene to investigate, but still had no clue.Even social workers near schools were brutally murdered, and these cases were classified as murders by the police.Yang Guangyao carefully inspected the scene and believed that the victim's death method was similar to that of black guy Tim.

At night, Yang Guangyao sat on the street and drank beer, then jumped into the river and swam to relieve stress.After landing, he continued to analyze the case and went to the autopsy room to conduct a full body examination of the deceased.During the examination, he found a pinhole on the deceased and decided to re-examine the other three deceased.

The next day, after Yang Guangyao saw off his wife and daughter, he began to investigate the case again.Through clues, he found Mai Zhihong, who had been sent to a mental hospital.After listening to Mai Zhihong's remarks, he was shocked and decided to trace the identity of the person who left the message.While observing Mai Zhihong in the interrogation room, another firefighter suffered a murder.After Yang Guangyao learned about it, he rushed to the scene.After returning, he found Mai Zhihong again to ask about the case, but the other party still said some incredible things.Soon, Mai Zhihong suddenly picked up a stick to hurt himself and called the police for help, which led to Yang Guangyao being framed.His superiors decided to stop his police work.Yang Guangyao angrily believed that Mai Zhihong was the murderer.After being suspended from work, he went home to visit his family, only to find that his wife and daughter were almost killed by a bomb because of him.

One rainy night, Yang Guangyao met an unidentified person in an underground passage and pursued him.He chased him all the way to the elevator upstairs in the heavy rain, but was knocked unconscious by a sudden attack.After waking up, the other party had disappeared without a trace.He wanders the streets looking for clues.

Yang Guangyao wandered around for a long time, but found nothing unusual.He instead returned to the hospital where his daughter was staying, intending to visit his family, but the doctor told him after examination that his daughter's name was not in the hospital at all.At this moment, he seemed at a loss. He hurriedly ran to the street, borrowed a dollar from passers-by, and then called a nearby street corner, but still got nothing.He even returned to his home, but there was no sign of his family.Unwilling to be reconciled, he came to the stairwell where he was tracking the man in black again, and used his memory to ride the elevator desperately, but found that he was always spinning in the same place, and even the doorman who watched the door had not changed.

The frustrated Yang Guangyao wandered aimlessly on the street and finally walked into a bar.He noticed that illegal transactions were going on inside, and the police had blended in, asking everyone to show their ID cards to prove their innocence.He subconsciously touched his pocket, only to find that his ID card was missing, so he fled in a hurry.However, the female police officer quickly caught up with him and after a fight, other police officers arrived at the scene and took him away in handcuffs.

In the police station, Yang Guangyao was in despair.Suddenly, a middle-aged man walked into the interrogation room. He took a closer look and found that it was Yang Yaoguang, who had been missing for more than 20 years.Yang Yaoguang also recognized Liu Weitao. After the two exchanged words, Liu Weitao talked about his experiences in the past twenty years, including the fact that Yang Guangyao's wife searched for him throughout Hong Kong.After hearing this, Yang Guangyao decided to continue looking for his family and solve these cases.Unable to defeat him, his boss agreed to let him return to the police station as an undercover agent.He changed his name to Lu Jiajie and restarted his undercover career.

At the police station, they received a new call, a case of drowning in a bathtub.The deceased's cell phone had been charged. Yang Guangyao launched an investigation as a police officer and found that this was not a simple accident, but a deliberate murder.At the same time, Mai Zhihong, who was at large, committed another crime.Yang Guangyao and others discussed this case and found that it was strikingly similar to the serial murder case twenty-five years ago.They suspected that Mai Zhihong had committed another crime, but when they arrived at the mental hospital, they found that he had escaped.Yang Guangyao angrily blamed Liu Weitao for failing to catch the suspect, but the police are currently helpless.