Yun ja Yu and Chae woon immediately have Mr Seo use his tech to discover the recent whereabouts of the staff and if anyone has withdrawn more than 30 million won. However, they aren’t able to get anything. She then makes Chae won spy on Mr Seo after he leaves thinking he might do something suspicious knowing she now suspects staff members.
Chae Won does as she says. Meanwhile, Yun ja Yu starts suspecting Chae won himself given that he knows so much about Citizenx, the Ransomware attackers. She has her AI Yeongsil tell her everything about him. That’s when she discovers he was a soldier in the terrorist attack that took place a few years ago. Meanwhile Chae Won calls her to let her know Mr Seo hadn’t done anything suspicious and had gone straight home but then she asks why he never told her he was a soldier at the terrorist attack. She demands him to come back to the company and the two iron it out.
Yun ja Yu accuses Chae woon of being a spy for the former president and his grandson who is now the current prime minister. But Chae won denies it saying he was scouted by her company. He didn’t come for the job and he didn’t think it necessary to tell her where he was from considering it was a traumatic event. However, he gets angry when she accuses him of planting the virus in her company. He says she should investigate her lab instead of him. When she leaves, Chae won secretly calls the former president Lee to tell him Yun ja Yu remembers him now. He wants a visitation with Kir, the man who claimed to be responsible for the terrorist attack and President Lee promises to arrange it.
President Lee calls his grandson prime minister Lee and tells him to arrange the visitation. Prime minister Lee is more concerned with news about the BF lab but he agrees immediately.
Very early in the morning, Yun ja Yu goes to the crime scene by the sea where her staff had the incident. She meets Chae won there and the two go to the company together. However Mr On meets Yun ja Yu in her office and sees her and Chae Won having breakfast. He suspects their relationship when he notices how tired they are that morning (thinking they must have done something else)
But he gets triggered when he discovers that she’s tracking the entire staff. Yun ja Yu has Ai Yeongsil tell her Miss Hong the accident victim’s whereabouts before her accident and it tells her she was last seen with Professor Kim, their research scientist. Yun ja Yu immediately starts to leave for Professor Kim’s place. Mr On tells her it’s no proof because Ms Hong usually dropped things off at Professor Kim’s place. When Mr On gets off at the elevator, Yun ja Yu confides in Chae won that she had known professor Kim for twenty years. They had set up BF together. However, Chae won tells her that time spent together doesn’t guarantee bonds of trust.
Flash back to the previous day before Ms Hong’s accident. She had visited Professor Kim to give him his things only to overhear someone rejoicing over money being paid to them. Professor Kim saw her at the door and started acting strange. Even following her to the car when she tried calling Mr On to tell her of her suspicions.
Next, we see him pushing her car into the river then visiting her secretly at the hospital when she was unconscious. He laments over why she had to appear at his house at that very hour telling himself he can’t get caught after fooling Yun ja Yu and getting the money. He then leaves before anyone can spot him. Yun ja Yu, Chae won and Mr On discover Professor Kim isn’t at his apartment. They call his line and when he answers, Yun ja Yu accuses him of planting the virus and stealing the money. Professor Kim doesn’t deny it but accuses her as well of killing his wife by performing a risky surgery on her when she had cancer. Yun ja Yu gets broken by this. Professor Kim cuts off his line and Yun ja Yu goes somewhere private to think. She calls prime minister Lee to get his assistance in issuing a no fly ban on Professor Kim. Prime minister agreed, but unfortunately professor Kim had already flown to Vietnam before then.
After breaking into Professor Kim’s apartment, Mr On gives Mr Seo his phone to check it out. Mr Seo is shocked Professor Kim turned out to be the Ransomware attacker. Noticing Yun ja Yu’s troubled mood while driving her to the company, Chae won stops at a snowy river side so she could take in the scenery. He also wraps her with a white cloth to keep her from the cold. (Cough…what’s going on?) He comforts her by insulting Professor Kim much to her amusement.
After a while, she decides to leave when she gets a call from her secretary. She asks her to investigate everything about Professor Kim. Chae won meets Kir in prison and asks him to divulge the real person who was behind him, who asked him to take the fall for the terrorist attack. He shows him the picture of an innocent kid who died during the attack and tells him his own family is doing well abroad. Kir, unable to handle his emotions, yells that everything is over but Chae won refuses to let it go.
He enters an old neighborhood asking a group of thuggish brokers that he’s searching for someone but they all run from him leading him into a trap. They start attacking him but Chae won’s martial skills are incredible. He holds one at ransom threatening to stab him and tells their leader to reach into his coat. The leader pulls out a letter seemingly surprised when he reads its content. It’s the prize money for finding Professor Kim. He tells them to find him since they have contact in Vietnam.
At a prestigious event, the prime Minister’s father Seonu Geum gives Yun ja Yu a tempting offer, to buy BF for thirty two trillion won. This leaves Yun ja Yu in a state of confusion. After she leaves, the prime minister’s father isn’t comfortable knowing that Chae Won, the soldier from the terrorist attack, is their spy. However, his son tells him that Chae Won is yet to get Yun ja Yu’s trust and assures him that they can always do away with him if he outlived his usefulness.
Meanwhile, Chae won is secretly investigating Professor Kim for Yun ja Yu without anyone else knowing. He calls her to let her know that Professor Kim is now in Cambodia, no longer Vietnam and sends her his picture but Yun ja Yu’s suspicions of Chae woon resurfaces as she wonders how he got such a picture. Chae woon notices her distrust of him and asks if he did something wrong but Yun ja Yu says that he couldn’t have gotten the picture out of pure luck and is suspicious how he always seems to have what she needs and be around when she wants him.
Chae woon finally comes clean, saying that he had offered thirty million won to brokers to find Professor Kim. Yun ja Yu feels bad for accusing him and offers to pay them herself. She then asks if he got the bruises on his face from getting beaten up by them but he replies that they fought. She then gives him a watch that allows entry to the building as a symbol of trust. However, the moment is interrupted when her AI Yeongsil reveals that Professor Kim died on a flight from Cambodia to Paris. (His drink was poisoned). Yun ja Yu gets clearly affected by this that Chae woon has to stop her from spilling hot coffee on her hand.
Protestors line up in front of BF shouting that Yu Ja Yu killed professor Kim because he had admitted to injecting bacteria into his culture fluid. Out of fear for her safety, Chae woon and the other bodyguard, Heosung, takes Yun ja Yu to his house. There, his cat is surprisingly affectionate towards her.
He reveals that he grew up in the house leading Yun ja Yu to get awkward. They end up having a conversation with Yun ja Yu stating they are both destined to suspect each other after he asks if she really killed Professor Kim’s wife. However, she doesn’t intend to stop running BF. Her secretary arrives with guns for Chae woon and the other guard in order to safeguard Yun ja Yu throughout the night.
As Yun ja Yu is driving to headquarters with Mr Seo, prime minister Lee calls Yun ja Yu to his residence but upon arrival, he had to leave to attend to an urgent problem. A large weaponry armory had been attacked and several weapons stolen. They are heading back when their car is ambushed by assassins pretending to be construction workers. A shoot out occurs and the four of them have to hide. Yun ja Yu immediately experiences a panic attack as she thinks back to the terrorist attack. Chae woon promises to protect her but gets shot trying to evade the assassins. The episode ends with Yun ja Yu crying to Chae woon to stay alive.
