The background of the case is set in 1994. In the tide of the times, people's hearts have fluctuated with it, laying a unique background for the occurrence of serial murders.The case was solved in 2012. Eighteen years have passed by, the aging police officers, the families of the victims who have emerged from grief, and the truth that has always been hidden in the shadows. The development of the case is full of a sense of fate and the times, and every detail touches the heartstrings of the audience.In this drama, we will follow the footsteps of police officer Lao Ran and his apprentice Zhao Gan'e, and go deep into the alleys to explore the traces of the serial killer.

In 2012, in a northern city, someone was stalking women with a laser pointer. Only Zhao Gan'e, a police officer in the archives office, realized that this was the serial murderer he was tracking 18 years ago.But no one believed him.He went to find a master who had been retired for many years and took care of dogs in the dog team.The master told him to get out.Back in 1994, Zhao Gan'e, who had just joined the Nanhuaishu Police Station, was determined to solve major cases and joined the criminal police team.

However, he met Ran Xi, an old film policeman who spent his life looking for dogs to push for work, as his master.Zhao Gange, who wanted to solve a major case, was run over in a small alley, vomited all over by a drunk, and locked in the house by a mentally ill lunatic.Ran Xi despises herself as a college student who is eager to prove her abilities.Madman Wu said incessantly that matter is conserved and humans are the same as ants. If you come, someone will die.The prophecy came true. At night, a female corpse appeared with her feet upside down in the well of Ran Xi's alley.

The female body was fished out, but Zhao Gange, who was determined to solve the major case, couldn't squeeze into the crowd and could only do some odd jobs.Later, when he saw the photo of the deceased, he discovered that he had also become a suspect---he had met Liu Ke on the night of Liu Ke's death.Zhao Gan'e was in a hurry, but his master Ran Xi just wanted to escape from the investigation work. But Ran Xi was a film police officer and couldn't escape no matter what.

In addition, Tian Hao brought his wife over to identify the body in the film to add to the confusion. It must be said that the deceased was their daughter who had run away from home.Both master and apprentice were depressed.At the meeting, it was learned that Liu Ke went out to answer the phone before his death. Zhao Gan'e was forced to admit that he met Liu Ke that night. Everyone in the criminal police team asked him angrily why he didn't tell him earlier. Ran Xi, a sharp-tongued man, kicked Zhao Gan'e away in public - he was actually rescuing Zhao Gan'e in disguise.

Although Zhao Gan'e reported the situation truthfully, Wang Lei, a classmate from the criminal police team, did not believe it. Fortunately, Ran Xi came forward to prove his innocence with evidence.Ran Xi wanted to go to the drugstore to check who in the film had not slept well recently and had taken sleeping pills. However, she accidentally discovered that her wife had purchased many boxes of couple's supplies, and she was confused about her life and work.

People in the area were panicking due to the murder case. Ran Xi, the original detective who handled the case, began to instruct Zhao Gange to conduct house-to-house investigations and take notes. Zhao Gange followed the nurse You Jia, but he was hit on the head with a stick as a gangster. The two met unexpectedly.The transcripts written by Zhao Gan'e were torn up by Ran Xi over and over again, and Ran Xi did not say what was wrong.Until the last time, Ran Xi told him that he had to use his brain when making notes. It turned out that Ran Xi had already seen the flaws in the notes and found the lying barber shop owner Er Yong.

Ran Xi revealed that Er Yong and Huang Hui, the mother of the deceased Liu Ke, had an affair at Er Yong's home. Er Yong also gave his wife sleeping pills every night. Huang Hui then committed suicide and was hospitalized and confessed at home that Liu Ke had followed her before her death. Ran Xi was satisfied. He found out why Liu Ke died in his film.

But Zhao Gan'e was dissatisfied. He discovered that the criminal modus operandi of the imprisoned criminal Meng Xiaoxing was similar to that of Liu Ke's case, and he proposed a serial murder conjecture, but Ran Xi objected.Based on the place where the body was dumped, Ran Xi speculated that the gang that stole manhole covers might be related to the case. After arresting the gang, Zhao Gange, although teased by the gang leader, still got clues to locate the garbage dump manager Lao Jian, and the police immediately began to stay on guard.

Zhao Gan'e went to the prison to meet Meng Xiaoxing with a letter of introduction. Meng Xiaoxing only told him that killing people was pleasurable and said nothing else.Zhao Gan'e came to invite You Jia to participate as a consultant but was rejected. However, he learned from the conversation that hydrogen peroxide can wash blood stains, and Qian Xiaolong's brother Qian Dalong had asked You Jia for hydrogen peroxide.The two went to Qian Xiaolong's house and learned that on the day Liu Ke was killed, Qian Xiaolong came home covered in blood and muttering strange words.

The criminal police team questioned Qian Xiaolong and Lao Jian separately, but one of them was really crazy and the other was pretending to be crazy, and made no progress.Criminal investigation experts speculated that the murderer might have sexual dysfunction, but due to a shortage of testing institutions, they could only rely on stamps to test whether the two had sexual dysfunction.At the same time, Ran Xi's son Ran Dongdong was harassed by Han Tao at school and received a love letter from his female classmate Lan Lan.

In the summer of 2012, while Zhao Gan'e was guarding his master from kicking him into the river, the two of them analyzed the case. They also met Director Zhu, who had been promoted to director.They asked Huang Hui about the whereabouts of Liu Ke's biological father, Zhou Weiping, and learned that Huang Hui had remarried and had a son, and had lost contact with Zhou Weiping.Today, 18 years later, only the police still care about the deceased.

Ran Xi learned from a neighbor that her wife Liu Beiping had made an Adam and Eve billboard, and became suspicious. She went to the store to meet the owner Wang Changju, and also saw the business that his wife had been doing secretly recently, including a lot of inflatable dolls and sex products.Zhao Gan'e secretly interrogated Meng Xiaoxing, who was arrested by the criminal police team, which once again aroused the anger of the criminal police team. Zhao Gan'e insisted that the suspicious points in Meng Xiaoxing's case were related to the serial murder case he was investigating, but was severely stopped by Ran Xi.

At this time, a beggar brought a wallet whose owner was Zhang Guodong. Ran Xi was worried about the case and family conflicts. At night, Qian Xiaolong fell from the mental hospital and died.

The deceased who fell from the mental hospital was identified as Qian Xiaolong. When the forensic doctor examined the body, he found Liu Ke's lost Walkman beside him, and Liu Ke's favorite song was playing. Zhao Gan'e also found important evidence in Qian Xiaolong's ant jar. Many evidences pointed to Qian Xiaolong. The criminal police suspected that he had committed suicide out of fear of crime and were preparing to temporarily close the case.But Zhao Gan'e didn't want to believe it. He refused to hand over the file and was even regarded as mentally ill.

He returns to the mental hospital again to look for clues.In order to find the murderer of Liu Ke, Zhou Weiping drove his car privately and broke Er Yong's leg.The 14 alleys under Ran Xi's care are in trouble again.Ran Xi didn't want to check anymore and just went home to repair the roof.At the same time, Ran Dongdong, who was running at night, saw the lost Tian Chang flashing past in the water tower window.

The next day, when Ran Xi was repairing the leaking ceiling, Zhao Gange came to visit. Ran Xi told him about his unbearable past. The relationship between master and apprentice further heated up, and Lao Ran decided to officially start investigating the case.Er Yong, who was retaliated against, came to the police station to report the crime, saying that he had seen Liu Ke getting into the limousine of Casablanca Cabaret owner Xiao Erhei, and Xiao Erhei became a new suspect.

Ran Xi and Zhao went to the Casablanca Cabaret to question Xiao Erhei. Xiao Erhei denied knowing Liu Ke and also mentioned that his rival, the crazy monk, liked female students. Ran Xi was wondering whether the other party was using her as a gunman.During the conversation, the crazy monk led people to attack and smash the karaoke hall. Ran Xi pretended to be from the Second Department of the Municipal Bureau and calmed down the situation, making the crazy monk lose money.

The next day, the crazy monk learned that Ran Xi was not from the Second Division, but an ordinary policeman from the police station, so he sent Fat Mao to the police station to bribe him and give him a bunch of bicycles.This sparked rumors that Ran Xi and the crazy monk were close friends.Zhao Gan'e suspected the crazy monk because of Xiao Erhei's words. Zhao Gan'e went to the repair shop to investigate, but was beaten. Ran Dongdong secretly sent school supplies to Tian Chang in the water tower.

Zhao Gange reported to Ran Xi the suspicious whereabouts of the crazy monk on the night of the incident, and threatened Ran Xi. If he did not bring the crazy monk back, he would go around and say that Ran Xi's apprentice was beaten.Ran Xi took a handbag, installed a water pipe, pretended to be a police gun, and used a trick to bring the crazy monk back to the police station for interrogation.The crazy monk Lao Jianghu revealed that Lao Ran had no evidence, but the interrogation time was only 24 hours.The crazy monk's younger brothers gathered in the police station to exert pressure.

In order to find evidence within time, Zhao Gangou found the mad monk's younger brother, Sha Mao, and used his own wounds to threaten Fat Mao to tell him some clues about the mad monk.Zhao Gange failed to find out about Liu Ke, but learned that the crazy monk had a girlfriend named Zhang Dan who had recently disappeared.

When Ran Xi mentioned Zhang Dan during the interrogation, the crazy monk had an abnormal attitude and suddenly became furious.Zhao Gan'e traced the whereabouts of Zhang Dan and found that she was the missing daughter of Zhang Guodong, and that one of the father and daughter was missing and the other was in another place.Later, the two found Zhang Dan's body near the beggar who had picked up the wallet.

The newly discovered female body was none other than Zhang Dan. The same soda bottle as in the Liu Ke case also appeared next to her body. All suspicions pointed to the crazy monk. However, during the interrogation, the crazy monk acted as if he had just learned that Zhang Dan had been killed.Everyone celebrated, but Zhao Gange had doubts. He always felt that something was wrong, and expressed his doubts to Ran Xi that the crazy monk was not the murderer.Ran Xi scolded him for being crazy, and said that she quit the criminal police because she was afraid of becoming a monster.

At the same time, Ran Xi's alley was in trouble because of his wife Liu Beiping.My wife’s “Adam and Eve” store was reported by foreign reporters and appeared on TV.Ran Xi felt extremely embarrassed.On the surface, Ran Xi is extremely disgusted with Zhao Gan'e's aggressive behavior, but secretly he helps the criminal police team to identify the crazy monk, on the condition that Zhao Gan'e can be transferred to the criminal police.The mad monk said nothing and needed a psychological breakthrough.

Ran Xi went to the crazy monk's mother's dumpling shop and accidentally discovered that there was a large amount of medicinal wine with therapeutic functions in the shop.Zhao Gan'e's small clinic confirmed that he had something unspeakable, and the crazy monk's mother revealed that the crazy monk had injured his lower body due to a fight.Back in the interrogation room, Crazy Monk finally told his love story with Zhang Dan. Although he found witnesses to prove that he was not present on the night of the crime, he felt that he was sorry for Zhang Dan.In 2012, the tattoo on the chest of Mad Monk, who was released from prison after serving time for other matters, had faded.

In 2012, with the help of Xiao Erhei, Ran Xi and Zhao Gan'e obtained key clues from Lili, a former karaoke waiter who had become Xiao Erhei's boss: Lili had heard from a psychiatrist that his patient had told about childhood experiences and the murder process, and the two immediately launched an investigation.Back in 1994, the murderer woke up from a nightmare and went out carrying a laser pointer and a dagger. He quietly listened to people on the street discussing his murder.

Zhao Gan'e was transferred to the Criminal Investigation Team as he wished, but he was still concerned about the serial murders in the area.During this period, a girl nicknamed "Little Manyu" came to Ran Xi and told Liu Ke that Zhou Weiping, Liu Ke's biological father, had severely injured Sha Mao and was looking for the murderer to take revenge.Lao Ran was so worried that he ignored Ran Dongdong's recent abnormality.Ran Dongdong persuades Tian Chang, who has run away from home, to move to his old house but is rejected. Liu Beiping reminds Ran Xi to pay attention to his son's college entrance examination and puppy love. Zhao Gan'e also encounters You Jia, who has not gone abroad because her fiancé abandoned her.

At night, Ran Xi wanted to follow Ran Dongdong who was running at night, but she left because of work.Zhou Weiping lit candles at home and said that Liu Ke told him in a dream that the person who appeared at 12 o'clock was the murderer, and determined that the murderer was related to Ran Xi.The alley was dark. As a female worker walked, a laser pointer lit up at her feet.The Alley Killer has arrived...

In 2012, Ran Xi continued to investigate the case with Zhao Gan'e despite being ill. Ran Xi was seriously ill at this time. He met Liu Ke's elderly grandfather on the way, and the two chatted. Ran Xi's memory seemed to be stuck in 18 years ago, and the old district had long been replaced by a gorgeous hotel. Only the victim's family was still waiting for the truth.Faced with an old, confused master who was about to lose his memory, Zhao Gange didn't know what the point of further investigation was.

Back in 1994, Zhao Gan'e accompanied You Jia to meet his fiancé's current wife. You Jia was heartbroken. Zhao Gan'e left after receiving the page. At this time, the reconstruction of the old district was in full swing.The crazy monk walked out of the detention center.The news that the crazy monk was released caused dissatisfaction among the neighbors. Everyone gathered at the police station to attack Ran Xi. They believed that Ran Xi had neglected his duty and demanded that the police officer be replaced.Zhao Gan'e refused to sort out the records in the criminal police team and focused on the serial murder case.

When the master and apprentice were eating at a stall, Zhao Gan'e proposed to go back to the police station, but Ran Xi refused.The next day, Ran Xi learned from the attacked female worker that the murderer made no sound while walking; Zhao Gan'e refused the criminal police team's business trip arrangement and applied to be transferred back to the police station.At night, Ran Xi got lost in the area where she had worked for many years, while Zhao Gange got the key clue from a casual remark of a girl playing on the roadside.It turns out that the alley killer was not discovered by stepping on the steps of the girl in front of him.

In 2012, the doctor told Zhao Gan'e that Ran Xi's time was running out. As a result, Zhao Gan'e had a bad temper, had a big fight with his boss, and smashed his office computer.Director Zhu asked him to receive psychological treatment. After 18 years, Zhao Gan'e and You Jia met again.

In 1994, Zhao Gan'e was transferred back to the police station from the criminal police team to pursue serial murder cases. The master and apprentice used clues to investigate shops selling laser pointers, and squatted on the roof at night to observe the situation in the area.Many days later, they saw the gentle Wang Kun sending You Jia home. Wang Kun's steps seemed to follow You Jia's.Zhao Gan'e followed Wang Kun, while Ran Xi found a mysterious man hiding in an alley and followed him. Finally, he found out in the water tower that the man was Tian Hao. Tian Hao said he was here to capture his daughter Tian Chang.

The darkness is approaching, and the two of them can feel that they are getting closer and closer to the murderer, but they have no clue who he is.In 2012, Ran Xi and Zhao Gan'e found the radio station "Intimate Sister" based on Lili's clues. During the period, they received a call from a stranger with a changed voice. On the phone, the man told about his murder process.The Alley Killer is still active.

In 1994, the two found the English training class where Zhang Dan had attended, met Wang Kun again, and found that Wang Kun used a laser pointer to teach everyone.Moreover, Zhao Gan'e discovered that the information of all students named Liu in Wang Kun's class registration list was missing.At night, when the two were squatting outside Wang Kun's home, the girl Li Jing threw a stone at Wang Kun's car. When Zhao chased her, Li Jing fell down and blood oozed from her body. 

In 1994, Li Jing told Ran Xi, Zhao Gan'e and You Jia how Wang Kun raped her in the hospital.A large number of nude photos of girls were found in Wang Kun's home. The tape recorder also played Liu Ke's favorite songs during his lifetime. All clues pointed to Wang Kun, but Wang Kun was nowhere to be seen.In order to capture Wang Kun as soon as possible, Youjia took the initiative to contact him. Zhao Gange hurried to Youjia's home after learning about it.

At night, Ran Xi saw the candlelight in the water tower on his way home. After entering, he found Tian Chang and Ran Dongdong. As a policeman, he sent Tian Chang back to Tian's house.Tian Chang listened to his parents' instructions at home, while Ran Xi had a conflict with Ran Dongdong because of Tian Chang.In 2012, Ran Xi listened to her close sister and the killer chatting on the phone, still racking her brains to figure out who the voice was.

But the murderer actually guessed that Ran Xi was nearby.He also provoked Ran Xi from the air.Ran Xi sat down on the ground angrily.Zhao Gange found the public phone booth from which the call came through the phone location, but the murderer had already left.

Ran Dongdong was looking for Tian Chang outside Tian Hao's shop. The exercise book left by Tian Chang before leaving was seen by Tian Hao. Tian Hao learned that Tian Chang and Ran Dongdong, who had run away from home, had stayed together.The suspicious Tian Hao and his wife insisted on taking Tian Chang to the hospital for a hymen examination. Tian Chang returned to school in a numb state after leaving the hospital.Liu Beiping discovered the cold war between Ran Xi and his son and wanted to mediate between them. However, Ran Xi left work in a hurry because Youjia received news that Wang Kun was planning to escape.

When Zhao Gange arrived, Wang Kun had already escaped, leaving only the injured You Jia.In the hospital, Ran Xi reminded Zhao Gan'e that if he was You Jia's boyfriend, the treatment might be unfair and suggested that he withdraw from the case investigation.However, Zhao Gan'e said that he and Youjia were ordinary friends and firmly stated that he must catch the murderer. All this was heard by Youjia in the next ward.In this way, the two of them broke off their fate.

Ran Dongdong and Ran Xi settled their differences and asked his father to hand over the exercise book to Tian Chang. Although Ran Xi agreed, Ran Dongdong found the exercise book in the trash can the next day, and then he realized that his father had lied to him.At school, the letter Tian Chang asked his deskmate to send to Ran Dongdong was discovered by the class teacher, who persuaded Tian Chang to concentrate on his studies.Both Ran Dongdong and Tian Chang were placed under house arrest and could not see each other.At night, Tian Hao locked the door of his house and Tian Chang recited English in his room. But early the next morning, Tian Hao discovered that Tian Chang had disappeared mysteriously and the reciting sound in the room was just a recording.When Ran Xi came home from the night shift, she met Ran Dongdong who was hurried out and found blood stains on his body.

In 2012, Er Yong told Ran Xi and Zhao Gan'e in his barber shop that he saw a woman who was very similar to the fugitive Zhou Weiping. Based on the clues provided by Er Yong, the two went to Zhou Weiping's house to stay.In 1994, a piece of clothing full of blood appeared in the area. Tian Hao immediately reported that Tian Chang was missing again. Everyone was worried that Tian Chang had encountered the murderer Wang Kun. It was confirmed that the bloody clothing was Tian Chang's school uniform.

The college entrance examination was about to take place. Ran Xi suspected that the blood stains on Ran Dongdong's body were related to the Tian Chang case, so she went to school and asked Ran Dongdong not to go home in the near future. Zhao Gan'e also learned from Tian Chang's school that she had written a letter to Ran Dongdong.At night, Tian Hao found the Ran family and asked Ran Dongdong to hand over Tian Chang. Ran Dongdong was taken to the police station for questioning. Ran Xi wanted to interrogate himself but was rejected by Director Zhu. In the end, Zhao went to school to pick up Ran Dongdong.

During the interrogation, Zhao Gan'e deliberately let Ran Dongdong see Tian Chang's investigation report, hoping that Ran Dongdong would admit that Tian Chang ran away from home and was not killed.In desperation, Ran Dongdong admitted that he had killed Tian Chang in order to buy time for Tian Chang to escape.Ran Xi angrily asked her son why he lied and said Tian Chang was killed by himself, but Ran Dongdong insisted on his own statement. Ran Xi understood that his son was delaying Tian Chang's escape. At this time, Tian Chang had successfully boarded the leaving train.Everyone found only exercise books in the well, but not Tian Chang's body.

In 1994, Wang Kun's traces were exposed. In order to completely clear Dongdong's suspicion, an impatient Ran Xi rushed out of the police station with a gun. Zhao Gan'e found out and chased after him.During the pursuit, Ran Xi lost control and pulled out a gun. Zhao Gan'e stepped forward to dissuade him. Wang Kun took the opportunity to hit Ran Xi with handcuffs and strangled his throat. At the critical moment, Zhao Gan'e shot Wang Kun.After Liu Beiping learned about Ran Xi and his son, he hurried to the police station. After seeing Ran Dongdong, he went home and waited. During this period, he received a call from Tian Chang.

Ran Xi, who was imprisoned in the radio room of the police station, used the radio to apologize to Ran Dongdong who was imprisoned in the room, explaining that she did not give the medicine to Tian Chang so that he could take the college entrance examination with peace of mind.In Tian Hao's store, Tian Hao and Zhou Weiping consoled each other for losing their daughter. Tian Hao told Zhou Weiping that the biggest suspect in his daughter's disappearance was Ran Dongdong.Zhou Weiping decided to avenge his daughter.Zhao Gan'e received news from Tian Chang through the local police station, proving that Ran Dongdong did not kill anyone, and Ran Dongdong was finally able to leave the police station.

Ran Xi, who was still imprisoned, asked Zhao to keep Ran Dongdong and Liu Beiping away from Tian Hao.When Zhao Gange arrived at Ran's house, he met Ran Dongdong who was out for a night run and hurriedly chased after him. However, Ran Dongdong was hit by a car driven by Zhou Weiping as soon as he reached the intersection. Zhou Weiping moved the unconscious Ran Dongdong into the car. Zhao Gange chased after Zhou Weiping's car and hit the demolition wall. After Ran Dongdong woke up, the three of them struggled and Ran Dongdong's head hit a sharp brick when he fell.Ran Dongdong died, but Zhou Weiping escaped.

In 2012, Liu Beiping took Ran Xi out of the hospital. After returning home, Ran Xi looked at Ran Dongdong's portrait and smiled and said that the father and son were about to meet.In 1994, his favorite Don Quixote was placed in front of Ran Dongdong's portrait. Everyone from the police station came to express their condolences. Zhao Gan'e came with an injury and apologized. Ran Xi just slapped herself silently, meaning that it was all your fault for trying to solve the case, and you didn't take good care of Dongdong.

The master and apprentice broke up tragically.After Ran Dongdong passed away, Liu Beiping and Ran Xi decided to move. On the eve of the move, Tian Chang called and Ran Xi informed her of Ran Dongdong's death.A year later, the demolition team came to the Nanhuaishu Police Station, and the police watched the police station building being demolished.No one cares who the murderer is.The clues disappeared down the alley.In 2012, Ran Xi and Liu Beiping, who were critically ill, watched the news broadcast report on the launch of Shenzhou-9. Ran Xi set the alarm clock and was still joking with Liu Beiping for 15 minutes, but when the alarm clock rang, Ran Xi was no longer breathing.

In the funeral home, Zhao Gan'e asked Liu Beiping to install cameras throughout the room, because Ran Xi told him before his death that people from the area would come on the day of the funeral, and key clues might be captured by then.But after checking all the videos, Zhao Gange still didn't find a breakthrough. Just when he was about to give up, a dog barking on the roadside made him notice the camera of the store at the door...

In 2012, Zhao Gan'e found Tian Hao and brought him back to assist in the investigation. In the interrogation room, Tian Hao initially avoided the important and trivial. He also lied and said that Ran Xi once said that the two biggest mistakes in life were to worship the wrong master and accept the wrong apprentice, trying to change the topic.Zhao Gan'e turned to talk about Tian Chang, Tian Hao's attitude gradually relaxed, and Tian Chang was outside the interrogation room door.Across the bars, Tian Hao and Tian Chang met again. Tian Hao still questioned why Tian Chang had been unwilling to contact his family for many years, repeatedly emphasizing that he and his wife had been working hard to raise and protect her.

Before Tian Chang left, Zhao Gan'e asked her mother Xiaomei if she had any strange comments on some of Tian Hao's behaviors during her lifetime. Tian Chang only said lightly that Xiaomei said before she died that Tian Hao was not what others thought.After Tian Chang left, Tian Hao recounted his interactions with Zhang Dan, Liu Ke, Qian Xiaolong and others many years ago. The context of the long-standing unsolved case gradually became clear. Zhao went to pay homage to Ran Xi's tomb, and Huang Hui also came here to pay homage.

Zhao Gan'e and You Jia met again and talked about the reasons for their separation. After leaving, Zhao Gan'e finally shed the burden of many years and sang with relief.According to Zhao Gan'e's later recollection, before Ran Xi's death, Tian Hao had found Ran Xi, who was seriously ill, and chatted with him alone for a long time. As for the content of the conversation, Ran Xi did not reveal much during his lifetime...