Do hyun soo the main character and his sister Do hae soo live with their father Do min seok.

Their father Do min seok makes metal crafts and is a serial killer. He kidnapped and kept his victims in the basement of his house/workshop.

Later he killed them and left a cut in their Achilles heal, put a dog collar around their neck and pulled out their nail of thumb and kept it as Souvenir.

These murders were called Yeonju City Serial Murders. He was never caught.

One day at do hyun soos school he comes across baek hee sung. Baek hee sung was on the terrace and threw a brick on a dog and killed it. The teacher had called his mother to school to talk about it. He lied and said that he didn't and he was just stressed about his exams. When hes waiting outside Do min seok tells him he must feel lonely as he hasn't found anyone like him. 

On 12th May 2002 the last of the 7 victims of  Do min seok is kidnapped. Her name was Jung Mi Sook. Her body was never found. 

When she was kidnapped there was a witness her name was Jang young Hee.

She remembered the kidnapping but since it was dark and the person was wearing a hat she never saw his face.

She files a complaint to the police immediately but once home she gets a call saying that the killer remembers her face and that she should be careful. So she tells the cops that she was drinking too much so doesn't remember anything properly.

That time when the police suspected Do min seok his son Do hyun soo served as an alibi because he was with his father the whole day. That means Do min seok had assistance of another person. That person was Baek hee sung.

Do min seok tells baek hee sung to turn himself in as this was his mistake ( that there was a witness to the kidnapping).

When Do min seok is leaving baek he sung attacks him from behind with a stone and kills him. 

Baek hee sung makes it look like suicide(we know this because thats what they say many times in the kdrama)

The village foreman takes the now orphan children in his care.

Now the village foreman wasn't some sort of saint. He and a group of villagers took Do hyun soo every night and did exorcism rituals on him. They said that his fathers spirit haunted him.

Do hyun soo started to believe them and he too felt that he was being haunted by his fathers spirit. All this took a huge toll on his mental health. His sister started to started to get worried about him. 

3 months later one day she goes and asks the village foreman to stop the rituals but he says no and is about to hit her. In self defence she accidentally kills him.

Do hyun soo comes to see his sister covered with blood. He takes the blame on himself. He tells her to change and burns her clothes along with his house where there were his photos and belongings. Everything that could connect to the siblings like DNA etc is burned.

Do hyun soo takes his bag and all his books that have his name written and intentionally drops them near the crime scene. He puts his fingerprints on the murder weapon and leaves it there too and runs away from the village. The cops conclude that he was the murderer of the village foreman and possibly the person who assisted Do min seok in those serial murders. The village foremans murder was called the geongri murder.

Do hyun soo has run away from the village and started working at a Chinese restaurant. Another person who works there was nam soon kil. Do hyun soo worked there from 2002 to 2005.

After that sometime in 2005 Do hyun soo is running away from an incident where Nam soon kil tries to steal from him. When he's running he gets in a car accident. The man who hit Do hyun soo was Baek hee sung(og)

Baek hee sung is the son of baek man woo and gong mi jaa. When he accidentally hits do hyun soo hes about to call an ambulance but do hyun soo tells him not to(as hes wanted man). Baek hee sung tries to call his father but he doesn't pick up the call. He goes home and starts to dig up a hole. Hes about to bury the unconscious do hyun soo. 

He doesn't know that he is Do min seoks son.

His mother meanwhile found a collection of human nails (the ones that were pulled out from the victims fingers) and a knife

His mother is shocked and scared and as she takes the knife is about to commit suicide she sees baek hee sung from the window digging and she sees the body of do hyun soo

She asks him what hes doing and he seems unfazed as if he's done this countless times before. She stabs him which almost kills him. Later we see that his father a doctor saved him (he goes in a coma). His parents hide him in thier house in a secret room so no one would ask questions as to what happened to him.

Now sometime between 2005 and 2006 do hyun soo takes baek hee sungs place. 

After that cha ji won meets baek hee sung (do hyun soo) and starts to have feelings for him. He rejects her at first buy eventually starts dating her.

They go on to marry and have a daughter. Ji won is a detective and knows reporter Kim moo jin. One day kim moo jin goes to meet Baek hee sung at his workshop to repair a necklace (cha ji won suggested he go to her husband to get it done). 

He recognises do hyun soo as kim moo jin used to date his sister do hae soo and also bullied do hyun soo.

Do hyun soo now baek hee sung ties kim moo jin and locks him in the basement for 2 or 3 days. Due to an incident he has to let go of kim moo jin.

He doesn't kill him but blackmails him that if he doesn't keep quiet baek hee sung will release the recording that kim moo jin had taken in school where he discovered the lair where do min seok kept his victims.

In the video we see that kim moo jin recorded the cages in do mink seoks basement. While recording he sees a sack bag that is moving. He realizes its a human being in it and at that same moment do mink seok  comes down. He says its an elk and Kim moo jin says ofcourse it is as hes scared.

Now next day a body is found at a Chinese restaurant. Naam soon kil the guy who worked with do hyun soo is killed in a similar manner of yeon ju city murders. Now the police (including cha ji won) note that the murder is similar not same. As some details like a cut in the Achilles heel was not revealed to public so this murder is a copy cat murder not suspect do hyun soo who is still on run.

Next day kim moo jin and baek Hee-Sung the next day come to an agreement to work together as baek hee sung needs to clear the name of do hyun soo so people don't try to look for him and Kim moo jin because he'll get a name.

The murderer turns out to be the husband of the last victim who was kidnapped but who's body wasn't found his name was park kyung Choon. He wanted to find her body and give her a proper burial. He thought that committing murders with similar pattern might make people look into do hyun soo again and that he might reveal his dead wife's body.

He then runs into do hyun soo and kidnaps him where he asks him if he was the accomplice of his father. He denies it. He says that he knows it was him because the fish keychain that do hyun soo had attached to his recorder was the same fish keychain that he had given his wife.

Baek hee sung suddenly remembers that at his father's mourning his sister came and gave him the keychain. He doesn't say that out loud.

Now baek hee sung is already tied and in an empty pool where water starts filling. Hes underwater and soon cha ji won who followed her husband through the gps chip she put in his watch because she previously suspected him to be somehow involved.

She saves him and park kyung choon is caught. Hes in the hospital where baek hee sungs father tells him to kill park kyung choon as he might reveal his identity (park kyung choon is pretending to be unconscious so police don't arrest him)

Baek hee sung goes to his hospital room and park kyung choon tells him to kill him as he deserves that.

The flashback reveals his sister said someone gave her this but as gold fish represents good luck she gave it to him. When park kyung choon asks why he didn't tell him that back then he says because he might have gone and harassed his sister.

Now further cha ji won suspects her husband but baek hee sung is unaware. He goes to kim moo jin and asks him to find his sister.

Baek he sung meets with his sister and tells her how he's been living for 18 years and hes married and has a daughter eun haa. She tells him that shes grateful that he took the blame for her back then. She asks him if he loves cha ji won. He says no he doesn't love her but he needs her.

He asks her about the keychain and she tells him someone gave her but she doesn't remember who. Cha ji won who had followed baek hee sung hears this.

Later to find do min seoks accomplice baek hee sung and kim moo jin go to a person who does human trafficking (they found out about him through a bar that so hyun soos father do min seok took him to once).

Do hyun soo says he'll pay him if he tells him the name of the accomplice. He agrees. When hes about to hand the photograph the dealer sang chul gets a call from baek hee sungs father and he says he'll pay double to kill the man making the deal (baek hee sung).

The dealer agrees and a fight erupts. Cops raid the place and sang chul runs away. Baek hee sung is discovered by his wife as do hyun soo.

Do  Hyun-soo asks why Ji-won stayed when she knew the truth about him. She asks if he really doesn’t know, and he doubles over, wailing that he’s sorry for causing her so much pain. 

Back at the real baek hee sungs place his mother removes the oxygen in order to kill her son but his father comes back home and he tries to do something in this process the real baek hee sung comes out of his coma. 

He says he can’t sleep because he’s scared that Hyun-soo won’t give his identity back, but his father promises he won’t let that happen.

The family is surprised when their doorbell rings it’s Hae-soo, who introduces herself and shows Baeks father he picture she printed of the silicone bracelet from his hospital, and how the accomplice was wearing one at her father’s funeral.

Baek tells Hae-soo that he’ll look into the people who volunteered for the event and got a green bracelet, though he makes no promises. 

Before Hae-soo leaves, Hee-sung’s mother asks if there was anything about the accomplice that stood out. Hae-soo recalls that the nails on his left hand were much shorter than those on his right.

She’s doesn't know that Hee-sung is in the next room, listening in and nervously biting the nails on his left hand.(This is where the accomplice is revealed in the drama)

We also see that it was Hee-sung who made the threatening call to the witness who saw him kidnapping Park Kyung-choon’s wife.

Back at do hyun Soos place, he tells cha ji won everything about his past.

Next day The maid asks to speak with Baek hee sung's mother. When they sit down together, she hands Mom a note, “I quit…Please transfer my severance pay and the money for my silence into my account by next week

The women are shocked when Hee-sung stands up. 

Dr. Baek gets home and when he sees the maid’s body, he finds Hee-sung and demands to know why he killed her. When Hee-sung explains, “She knew too much,”

Hee-sung had contacted Sang-chul, who insisted he didn’t tell Hyun-soo anything other than that someone paid him to kill him.

Hee-sung had ordered Sang-chul to stay out of things from now on, and he was the one to tell his parents that Hyun-soo was setting a trap (moment Sang-chul showed up at the summer house, Hyun-soo would know exactly who sent him.)

Instead of going to the farmhouse do hyun soo and ji won go to baek hee sung's house and send cops to the farm house in order to catch sang chul.

While they’re all inside, Hee-sung plants hairs from the dead housekeeper in Hyun-soo and Ji-won’s car so as to make do hyun soo the culprit of the maids murder.

Later that night, Hyun-soo receives a call from someone 

He says he’s a fan of Hyun-soo’s art, but Hyun-soo hears the call for the threat that it is, unaware that it’s the real Baek Hee-sung on the other end.

Hyun-soo traces the call, which locates at a pay phone in Makmun-dong. He goes there but the area is deserted, and when he calls the owner of a car parked nearby (their number is on their dashcam) to ask if he can look at the video footage, she’s on vacation. 

Hyun soo returns to the pay phone and this time he sees a message written on the glass: Hide and seek! I can see you, but you can’t see me.

Some volunteers find the body of the dead housekeeper in a shallow grave.

Jae-sub has called Ji-won to the scene. 

The housekeeper’s notebook is found beside her body, and the most recent notes show that things were not well with her employer.

In one note to Hee-sung she’d mentioned his parents by name, giving Ji-won pause just as they get the call that she’s been identified.

Additionally a fingerprint was found on the tape that was on her body, but despite it being a complete print, there’s no match in the database.

This means the killer is an adult who has no government ID. Ji-won’s worst fears are confirmed when she learns that the dead woman was her in-laws’ housekeeper, and all she can think of is how Hyun-soo left the house last night.

Ji-won takes a copy of Hyun-soo’s fingerprint from their house. She compares it to the unmatched print from the housekeeper’s body, and it’s a perfect match. 

Do Hyun-soo calls Sang-chul to ask him to meet. But Sang-chul left Mi-sook alone with his phone, so when it rings, she’s the one who answers.

She tells Hyun-soo her name, so he asks where she is, but she only has time to say there are a lot of trees before Sang-chul returns and hangs up the phone.

Jae-sub shows up with the entire team, but the studio is empty. They check the CCTV footage, and see that it’s been unplugged. Rewinding to the point where Hyun-soo takes Ji-won hostage, they watch in horror as Hyun-soo directs Ji-won to disconnect the CCTV feeds.

As soon as the cctv is turned off they run away and do hyun soo goes to find jo mink seok.Detective cha says shes fine and not hurt when they find her in a hotel cuffed to a table.

 

Eun ha and do hae soo go to her place to take eun has clothes but baek he sung is waiting there. Eun ha locks herself into her room and baek he sung mistakens do hae soo as cha ji won and kills her

Now Do hyun soo is in the basement of his father and jung mi sook. He puts a new lock on her cage and gives the key to her. When the negotiations between baek hee sung and sang chul are over he tries to open the lock but can't. Do hyun soo attacks baek hee sung from behind and ties him to a chair.

He asks him for his phone and finds it in his pocket where ji won's ID card was there. He loses it thinking that ji won is dead. He tries calling her but since its an unknown number she thinks it might be reporters and doesn't pick up. Hes about to kill him when he breaks free and runs out. 

The cops solve the case and come to the conclusion that baek hee sung is awake and his parents helped him with the murder of the maid. 

Kim moo jin is at their place at that time and ji won calls him to warn. He doesn't take the warning and goes around the house to confirm about baek hee sung. 

His parents finally give in. Now on the other hand Do hyun soo is about to kill Baek hee sung but the cops arrive just in time

Baek hee sung takes the gun from the cops and shoots at ji won but Do hyun soo takes the bullet.

Episode 16 of the flower of evil is the final episode.

Its been 4 months after the shooting incident and do hyun so is now out of coma.

The court trials have begun and do hae so is in jail. For her to prove it was self defence she needs witnesses. The village foreman had a nephew who is scared to testify but tells cha ji won the truth. He used to spread false rumours about do hyun soo like how do hyun soo was possessed by his fathers spirit. 

He used to cut open a chicken and leave it on the road at night and in the morning when the villagers gathered he would blame do hyun so thus making the villagers sure that do hyun soo needed exorcism. 

The village foreman had taken do min seoks Inheritance and therefore told his nephew that he'd pay for his tution if he spread those rumours.

The court lets do hae soo go as they said it was an act of self defence and that she was a a minor at that time. Hae soo soon decides she wants to start over again and will leave Korea for further studies.

Baek hee sungs father is in hospital because hes mentally unstable and his mother is in jail.

Do hyun soo, cha ji won and eun ha reunite and have a new beginning as a family.