In the middle of the road, police officer Chia-Hao lays on the ground, bleeding and having flashbacks of his childhood. There's an image of a woman sitting in front of him looking quite blurry, but the other memories are fine. Chia-Hao explains that he's been able to see ghosts since he was a little kid, and he's been bullied a lot for it. This started half an hour ago. Chia-Hao and his companion Chieh are watching over a closed road. Chieh thinks Chia-Hao would have a better life and make more money if he used his abilities to be a medium instead of a cop, especially considering he keeps getting in trouble on the job, like the time he pushed a ghost out of a car's way.
When Chieh gets off the road to relieve himself, Chia-Hao gets distracted and a car passes past him, so he rushes in his own vehicle to stop it. The driver, Hei-Gou, apologizes and explains he's in a hurry because he wants to reunite with his family after not seeing them in weeks, convincing Chia-Hao to let him go without paying a ticket. However on his way back, Chia-Hao notices the taillights are off and when he opens the trunk, he finds a wallet covered in blood. Before he can do anything about it, tough, Hei-Gou appears next to him and hits him, making him fall to the ground. Chieh shows up and tries to arrest the man, but Hei-Gou steals his gun and kills him.
He also shoots Chia-Hao on the shoulder, but when he's about to fire again to finish him, the ghost of his victim Ya-Hui shows up to slow him down, giving Chia-Hao the chance to take out his own gun and shoot Hei-Gou, taking us back to the beginning of the story. The last thing Chia-Hao remembers before passing out is the ghost pointing at the bloody wallet. A few days later, Chia-Hao is congratulated by his superiors for having caught a highly wanted criminal. However, the higher-ups aren't happy with the part of the statement that says he was helped by a ghost and they think Chia-Ha's delusions are to be blamed for Chieh's death. Not wanting to lie about it, Chia-Hao refuses to take out that part of the story and gets fired. Chia-Hao doesn't know what to do with his life now.
Luckily for him, he's approached by Mr. Chang, the head of a secret police unit that is accessed through an elevator that everyone believes to be broken. Mr. Chang saw Chia-Hao that time he pushed a ghost out of a car's way and is impressed by the boy's respect towards the ghost that saved him, so he has the perfect work for him. After Mr. Chang presses two elevator buttons to access a secret floor, Chia-Hao arrives at the Ninth Precinct, a special unit in charge of dealing with ghosts that still wander the Earth after dying. Chia-Hao is confused because he doesn't know how he could help the ghosts when he can see them but not hear them, but Mr. Chang tells him he'll learn to hear them when the time comes. At that moment, the ghost of Chieh shows up, and Chia-Hao apologizes to him, promising to burn a paper doll in his name before he watches the spirit move on to the afterlife.
Next, Chia-Hao meets Hsueh, an expert medium that allows spirits to possess her and often drinks a lot to deal with it. Their introduction is interrupted when a new mission comes in, so Mr. Chang shows Chia-Hao the tools of their trade. The peachwood umbrella has incantations on it to keep bad spirits away and protect good souls. The incense burner allows them to be understood by the ghosts, kind of like a telephone. And the guns don't use normal bullets here, they are loaded with sacred water that can dispel evil spirits - these must only be used with the unsalvageable ghosts. There aren't normal badges either, the symbol of the Ninth Precinct is a ring that Mr. Chang wears around his neck and Chia-Hao will have to work hard to earn his own. The first case is about a haunted home in the city. A young woman's radio keeps turning on by itself, and the cupboard door is often opening on its own too, letting candy fall to the floor. At night, she sees the spirit of a kid appearing around the house, and while sometimes she tries to blame it on bad dreams, she finally accepts it as truth when she wakes one morning and finds the kid holding her. After they hear her story, Mr. Chang and Chia-Hao ask the house residents to leave so they can do their investigation. Chia-Hao immediately reaches for the cupboard, and when he opens the umbrella, the ghost of the kid appears next to him. In order to communicate with him, Mr. Chang takes a piece of candy and puts it next to the incense, allowing him to talk to the boy and understand what he's going through. It turns out his parents didn't have the ritual done properly after the boy's death, and now the kid's soul is trapped here, longing for his mother's return.
The ghost never intended to scare the lady, he's been longing for the warmth and attention of a mother. Mr. Chang promises the kid he'll see his mother again, then uses the umbrella to catch him inside like a Pokémon, this way they can take him to the office to help him move on. Meanwhile, at the Sun General Hospital, Dean Yu-Shu is practicing a sales speech about her rejuvenation treatment when her assistant interrupts her to inform her that Councilor Lin was critically injured in a car accident. Because it's very important to keep a good relationship with politicians, Yu-shu orders her assistant to give Lin her turn in the treatment. She also reminds him not to hire another useless thug like Hei-Gou again or he'll have to face the consequences. When Mr. Chang and Chia-Hao return to the office, Hsueh informs Chia-Hao that there's a female spirit following him yet refusing to show herself.
Chia-Hao wonders if it's the spirit of the woman he helped wanting him to solve her case, but Mr. Chang forbids him from getting involved: catching criminals is the job of the normal police, the Ninth Precinct only deals with ghosts. Still haunted by the blurry memory of a woman, Chia-Hao decides to ignore Mr. Chang's orders and returns to the road where they caught Hei-Gou. He encounters Ya-Hui's ghost and, after lighting the incense, he thanks her for helping him and shows her he still has her wallet. With a nod, Ya-Hui confirms she wants help, and Chia-Hao accepts her case. A few moments later, Chia-Hao breaks into an apartment Ya-Hui has taken him to. Because he's distracted, he doesn't hear someone coming and is knocked out with a pan hitting his head. When Chia-Hao wakes up handcuffed to the chair, he meets the owner of the apartment, journalist Ju-Hsin. To prove his story, Chia-Hao shows her Ya-Hui's ID, then points at a box Ya-Hui was also pointing at.
Inside, Ju-Hsin finds Ya-Hui's journal with a picture of them together. Now she believes that Chia-Hao can see Ya-Hui, so Ju-Hsin explains her friend has been missing for over a month and needs help finding out what happened, causing Chia-Hao to accept to team up with her. The next case for the Ninth Precinct is a house with weird noises and constant shaking of furniture. The old man that has been hearing all this is actually the ghost that is haunting the place - he isn't aware he's dead and the voices he's heard are the new residents of the house. Now that the cops are here, the old man approaches the shelves, as if needing something from them. Chia-Hao checks them out and finds a hidden compartment with a box inside containing various items that used to belong to the ghost's daughter, like a hair tie. They need to find the daughter to fulfill the old man's wish and help him move on.
At that moment, Hsueh is possessed and gets a vision of the countryside, revealing the daughter's location. When they get there, they find the area is crowded with ghosts of young girls wearing the same gown, so Chia-Hao uses the hair tie to find the daughter they're looking for. Then, he opens the umbrella to release the old man's ghost, thus he finally reunites with his loved one. More surprisingly, Ya-Hui's ghost is there as well, and her gown matches the others. Later, when the normal police come over and start digging, they find the bodies of all the ghosts, Ya-Hui included. The matching gowns clearly indicate they all were killed by the same person and Chia-Hao wants to find them, but Mr. Chang once again reminds him he mustn't get involved.
To prove his point, he shares the story of a Ninth Precinct officer that tried to get involved and got his wife killed in a car accident as result, which made him lose his relationship with his daughter. Back in the hospital, Yu-Shu is in a hidden room where she's treating Councilor Lin by putting Hei-Gou's body in a pool. She also orders her assistant to find another one, or she'll be using him next. Meanwhile, Chia-Hao gets a call from Ju-Hsin, who saw the news about Ya-Hui's body and has been reading her diary. It turns out Ya-Hui had been pregnant and Councilor Lin was the father. She had an appointment with Yu-Shu for an examination, but that's when Ya-Hui disappeared. Ju-Hsin did some digging and discovered all the victims had been to the Sun General Hospital, which explains the matching gowns. Ju-Hsin and Chia-Hao decide to pay Yu-Shu a visit, but Yu-Shu pretends to be innocent and not to understand what they're talking about when mentioning the victims' gowns.
When it comes to Ya-Hui, Yu-Shu does admit she did examine her as a favor to Councilor Lin, but that's it. Ju-Hsin is sure Yu-Shu knows something, but there's nothing they can do without a warrant, so they decide to leave. On their way out, Ju-Hsin sees there are security cameras around and gets an idea. She bribes the guard to let them access the camera footage and finds many interesting things that she copies on a pendrive: Councilor Lin is showing no scars from the accident, Ya-Hui came to the hospital and never left, and Hei-Gou came shortly after her. Yu-Shu is doing some research of her own as well: her assistant confirms that Ju-Hsin's date of birth fit the treatment's criteria perfectly. Considering her a worthy sacrifice, Yu-Shu summons an evil spirit that is sent to catch Ju-Hsin. Back to Chia-Hao, he accepts Ju-Hsin's invitation to come to her place to share a drink. While they're chatting, he spills some wine on his pants, so he rushes to the bathroom to wash them.
At that moment, the lights go off and Yu-Shu's evil ghost appears. Chia-Hao quickly jumps into action, grabbing his gun but leaving his pants behind as he tries to deal with that blurry memory of his becoming more clear and showing the ghost of a woman. When he finds the ghost, Chia-Hao tries to shoot him, but the spirit moves too quickly and after a few spooks, it leaves because he knows he can't go against a cop. Suddenly, the apartment door opens and Mr. Chang shows up, not happy at seeing Chia-Hao in his underwear because Ju-Hsin is his daughter. Mr. Chang tries to question what's going on, but Ju-Hsin doesn't allow him to say anything: she doesn't understand why he had to show up now after years of not talking to her. Wanting some time alone, Ju-Hsin kicks both men out. When they reach the streets, Mr. Chang refuses to hear Chia-Hao's explanation and shoots him with some sacred water bullets. Later at the office, Mr. Chang hits Chia-Hao for investigating against his wishes and dragging his daughter into it.
After Mr. Chang leaves, Chia-Hao wonders why they're police officers if they can't bring justice. Hsueh explains that the cop from the story that lost his wife is Mr. Chang himself, so he wants to protect his officers from making the same mistakes he made. Meanwhile, Mr. Chang calls Ju-Hsin to try to get her to drop the case, but Ju-Hsin is still angry with him for having left after her mom died. At that moment, Hsueh gets possessed and writes "disaster" on a sheet of paper while Ju-Hsin notices something curious on the security footage: Yu-Shu's shadow has horns. Before she can do anything about it, Yu-Shu's assistant shows up with two thugs and kidnaps Ju-Hsin.
Mr. Chang quickly realizes something is wrong on the phone and goes to his daughter's apartment, only to find all the clues she's been gathering and the paper dolls he had gifted her years ago. Deciding to break his own rules, Mr. Chang goes to the hospital and, after beating up the guards, confronts Yu-Shu. He asks to have her daughter back in exchange for the evidence she's gathered, but Yu-Shu laughs as she reveals her black eyes and shows Mr. Chang that Ju-Hsin will be the next person to be sacrificed. Then, she uses her black magic to capture Mr. Chang in order to send him to the roof, promising to make it look like he jumped of his own accord.
The police find the body a few hours later and the incident appears all over the news, it seems Yu-Su has faked some papers and now everyone believes Mr. Chang had been going to the hospital for months for mental problems. Everyone in the Ninth Precinct is grieving, but the one that got hit the hardest is Hsueh, who shares her story with Chia-Hao. As a kid, she had two dads: her biological father, who died when she was three, and then the man that adopted and liked to beat her up. One day, she got tired of it and ran away, only to pass out in the middle of the road. She woke up later at a temple where she lived until she turned eighteen and Mr. Chang recruited her for the Ninth Precinct - that's also when she learned Mr. Chang had been the one that found her and took her to the temple in the first place. In return, Chia-Hao shares his own story. He had two mothers because a fortune-teller told his dad that he would have two wives, so he married Chia-Hao's ghost mother to fulfill the prophecy. Chia-Hao was the only one that could see her, but he still loved her with all his heart, and the blurry memory is of her watching over him when he was sick.
Unfortunately, Chia-Hao got bullied by other kids for his powers, and when he couldn't take it anymore, he started to ignore his ghost mother until she disappeared. Since then, he can't hear ghosts anymore. This is why Chi-Hao wants to find justice for the ghosts he encounters nowadays. Hsueh finally understands what's like to want to help the ghosts, deciding to ignore the rules and team up with him to bring down Yu-Shu. They start by ambushing the assistant at the hospital parking lot and kidnapping him to bring him to the office. The assistant refuses to talk, thinking Chia-Hao doesn't have the guts to shoot him, but Hsueh has changed the bullets in the gun and Chia-Hao ends up accidentally shooting the man on his shoulder. Hsueh then grabs the gun and puts it in the assistant's mouth, which prompts him to talk. Yu-Shu has been using people that were born on the same date to keep herself and her politician friends forever young and prolong their lives. The treatment needs a ritual and a sacrifice, but the most important thing is the medium. Hsueh and Chia-Hao armed themselves to the teeth, and Chia-Hao hangs one of Mr. Chang's paper dolls around his neck as a good luck amulet.
Then they drive to the hospital, where they easily beat up the guards before finding the secret room with the altar holding an unconscious Ju-Hsin. Yu-Shu hears them arrive and interrupts her prayers for the devil to begin shooting at them, so Chia-Hao hides behind a statue and Hsueh goes behind a door that accidentally locks behind her. Hsueh now finds herself surrounded by ghosts that she proceeds to fight with her sacred weapons. It's a quick, clean fight, but after all the ghosts are exorcised, one more appears: it's Hsueh's abusive dad. Scared, Hsueh steps back and closes her eyes to concentrate, reminding herself she's not a kid anymore. Meanwhile, Chia-Hao and Yu-Shu continue to fire at each other, but Chia-Hao's bullets never land because Yu-Shu has a magic shield around her. When Yu-Shu throws Mr. Chang's ring at him, taunting him, Chia-Hao gets an idea. He puts down his guns and approaches Yu-Shu with his hands up, pretending to surrender.
Once he's close enough, he spits at her the sacred water bullets he's been holding in his mouth at the same time Hsueh takes a quick sip of her drink and spits at her father's ghost to destroy him for good. Yu-Shu pushes Chia-Hao back by shooting his shoulder, but it's already too late: her body is now revealing its real age. As Hsueh predicted, the medium is the most important part of the ritual, so the dark energies around Ju-Hsin disappear. Yu-Shu tries to shoot Chia-Hao again with the little energy she has left, but then, Mr. Chang's ghost appears to distract her, and Yu-Shu finally drops dead. He points out that this is the second time he's saved Chia-Hao's life, because it was his amulet that guided the bullet to his shoulder.
There's also a very special change happening: Chia-Hao can finally hear ghosts again. While Hsueh finally gets the door open, Mr. Chang takes out Ju-Hsin from the ritual pool and talks to her until she wakes up. Sadly though, she doesn't have the ability to see her dad. A few days later, Ju-Hsin holds a funeral for her father, and Chia-Hao attends while wearing Mr. Chang's ring around his neck. Seeing his daughter bring the paper dolls she held so dear allows Mr. Chang to move on in peace. Sometime later, Chia-Hao goes to his old house to revisit his childhood memories, which allows him to finally see his ghost mother again. The two of them reconcile, and the lady finally gets to move on as well.
Politicians appear on news shows denying ghosts are real and any connection to the mysterious Yu-Shu case. While the officers are watching this report at the precinct, Hsueh suddenly gets possessed and floats up in the air, announcing with a deep voice and white eyes that the end has come. Then, she falls to the floor, and the cracks forming around her form a pair of wings.