Episode 5 of "Phantom Lawyer" starts with I-rang interviewing his new ghost client and signing a contract. This time, the client is a scientist, Dr. Jeon Sang-ho, who doesn't believe in ghosts. He soon possesses I-rang and goes into full scientist mode, writing equations on his board that prove that ghosts do not exist.
Bong-soo and the priest, Ma Tae-oh, are in the office, so Tae-oh uses some holy water to bring back I-rang. It doesn't take long to figure out who the ghost is, since he's a famous scientist who has won the award for "Scientist of the Year" three years in a row and was next in line to become the leader of life sciences in Korea.
Meanwhile, Na-hyun is updating a team of defense lawyers at the Taebaek law firm since they are hired to defend the accused, Sang-ho's wife, Kim Su-jeong. She is the daughter of an influential member of the science community, Chief Kim Tae-jun. During the first trial, Su-jeong was acquitted for lack of evidence, but the prosecution team appealed, citing that they had found new evidence. Na-hyun's team has no idea what it might be, so she schedules a visit to talk to Su-jeong before the trial.
At I-rang's office, a quick internet search reveals Sang-ho's full name and date of birth. Once I-rang says that to them, all the memories come flooding back, and he thinks that his wife killed him.
I-rang asks Sang-ho to recount what happened on the day he was murdered. In a flashback, after they sneak into his home that night, he comes back from work and gets into a heated argument with Su-jeong. He lies to I-rang, claiming it was a normal lovers' quarrel, while the truth is that Su-jeong was quite frustrated with him for not getting any results, and Sang-ho decided to quit the research altogether.
The research findings must hold immense significance for Su-jeong, as her disagreement with Sang-ho culminates in his storming off to his home office. He remains there, isolated, until he hears Su-jeong's footsteps as she climbs the stairs to bed. Seeking solitude, he ventures to the bathroom for a wash, only to be ambushed from behind. The foggy mirror in the bathroom prevents him from seeing the assailant's face, leaving him uncertain whether it was Su-jeong or not.
Meanwhile, Do-hyuk receives information about I-rang from his assistant, learning that they will face him in court alongside Glory Entertainment's trainee, Emma. Simultaneously, Na-hyun spends the night preparing for the trial, receiving a call from her father that reveals their distant relationship.
At I-rang's home, Sang-ho keeps him awake all night, reflecting on how he failed to support his wife when she was alive and doesn't want to further complicate her life now. He shares how his preoccupation with work, even at home, made him neglect her. When their son was born, he was afraid of dropping him, so he never helped her take care of him. She suffered from post-partum depression and once attempted suicide. He feels indebted to her and doesn't want her to go to jail, even if she's the killer.
The next day, before court, I-rang runs into Na-hyun. She had been working all night and hadn't noticed the hair coil still stuck in her hair. I-rang pulls it out to help her and hides it. Na-hyun gets angry at him for touching her hair and mentions that Sang-ho was murdered in the bathroom - a detail that hadn't been revealed in court yet. When she asks about his informant, he insists it was a ghost, making Na-hyun so angry that she asks him to pretend they don't know each other henceforth.
During the court session, prosecutor Kim presents new evidence that Sang-ho was murdered in the bathroom. The analysis of blood spatter suggests that the person who killed him was taller and stronger than Su-jeong, implying she had an accomplice.
Suddenly, Su-jeong changes her testimony and confesses to the murder, insisting that she did it alone without any accomplices. She is arrested and taken to prison, awaiting a murder trial. Meanwhile, Do-jyung continues his investigation into I-rang and speaks with Emma, asking if she noticed anything strange about him. She tells him that he didn't act like Su-a, but during their confrontation, he was Su-a.
Do-jyung remembers Gi-cheol had said something similar about I-rang's personality change and becoming Gang-pung. Later, he checks up on his office location and discovers it was formerly a Shaman's office.
Elsewhere, Na-hyun shows up at I-rang's office seeking the truth about his informant. As usual, he tells her the truth, but she doesn't believe him. He tries to explain, showing her how Sang-ho possessed him and wrote the scientific equations on his board. He begs her to investigate and compare the handwriting on the board to Sang-ho's.
Na-hyun decides to visit Sang-ho's office, and his colleague Gu Hyo-jung offers new insights into the case. It turns out that Tae-jun targeted Sang-ho for an arranged marriage with Su-jeong. He wanted his expertise to research a cure for his wife, who was suffering from a rare disease called 'Concello'. This disease affects the brain, and his wife has lost all memory of anyone except Tae-jun.
From Hyo-jung, Na-hyun learns that Su-jeong confessed to protect her father for her mother's sake. Her father is the only one who can take care of her. He thinks that he killed Sang-ho for abandoning the research and not finding a cure for his wife despite all the resources he put into him.
Hyo-jung shows Na-hyun to Sang-ho's office, and she notices the similarities in handwriting. Meanwhile, I-rang's new plan to help Sang-ho is to find his body, which is still missing. Sang-ho remembers a potter's field next to the lab. It's a hill surrounded by dense trees that was rumored to be haunted, so not many people visited. He and Su-jeong didn't believe in ghosts, so they frequented the place when they wanted to be alone.
I-rang and Sang-ho head out to the Potter's field, unaware that Do-hyuk is tailing them. They follow the clues and find the body buried in a shallow grave. Seeing that the body was dragged through the forest, Sang-ho deduces that Su-jeong didn't have the strength to carry him out of the house, to the car, and all the way to his shallow grave. He realizes that she wasn't the killer. The realization of who it could be fills him with rage, and he possesses I-rang.
Elsewhere, Kyung-hwa's instincts tell her that I-rang might be in danger. She learns from Bong-soo that he went looking for Sang-ho's body just as Tae-oh shows up at their house. They all head out to find I-rang.
Na-hyun arrives at I-rang's office, offering a profound insight: if the hypothetical scenario of Sang-ho being alive were to unfold, he would undoubtedly confront his murderer, Kim Tae-jun. Kyung-hwa appeals to her for assistance, and she drives them to his house. Simultaneously, Do-hyuk discovers the body in the woods.
Possessing I-rang's body, Sang-ho heads to Tae-jun's residence. He confronts him for the murder and for leaving Su-jeong in prison. Just then, his son wanders outside, further fueling Sang-ho's rage. When Tae-jun carries the child back inside and locks the door, Sang-ho attempts to break it open with a stone.
At the episode's climax, Kyung-hwa embraces I-rang as raindrops bring him back to reality. Suddenly, Prosecutor Kim and his team arrive to arrest him for Sang-ho's murder. They've discovered the body and his DNA on it, as well as on the nearby discarded gloves. Kyung-hwa tries to protest the arrest as Na-hyun watches in confusion.
