Delightfully Deceitful episode 1 begins with someone burning down a house. Elsewhere at a prison, a young lady called Lee Ro-Um, is not helping her prison mate clean their cell. One of her comrades gets angry about her not helping, and confronts her.
One of the correctional officers comes to see what the matter is. Lee Ro-Um’s prison mate who confronted her goes to report her for helping out with the cleaning. But when she turns around, she sees Lee Ro-Um cleaning, making her look like a fool for the report. Lee Ro-Um is actually in prison for killing her parents.
Elsewhere at Park & Cue Law Firm, the CEO, Park Kyu, is trying to convince the law firm’s Chairman, Jung’s son, why one of their lawyers, Han Moo-Young is the best one to handle his case. Chairman Jung’s son got into an accident while in a taxi and broke his arm.
Meanwhile, Moo-Young is in court representing a card sharp caught using his skills to win a game at a casino illegally. Moo-Young proves that the card sharp did what he did to help a woman he had an interest in, recover the money she lost in the gambling game. The judge decides to suspend the card sharp’s jail sentence for three years, thanks to Moo-Young.
As Moo-Young is leaving, a local media reporter, Woo Young-Ki, tries to ask Moo-Young for an interview, but he declines. Moo-Young bumps into a young boy, Byeol, and his mum. Judging by how Byeol’s mum is talking to Moo-Young, he was representing her case then dropped it.
Chairman Jung’s son voices his doubts about Moo-Young representing him in court as he’s picky with his clients and rude, he’s also been nicknamed “vampire.” Back in court, as Moo-Young is getting into his car to head back to the law firm, he spots a woman called Seo Gye-Sook, holding up a sign demanding justice for her son, Too Myung-Hoon, who died suspiciously under his adoptive parents’ care.
Back at Park & Cue Law Firm, Park Kyu introduces Moo-Young to Chairman Jung’s son. It turns out he didn’t hurt his arm, he just wants to take the taxi driver to court for no reason. However, Moo-Young still agrees to represent him in court anyway.
Later, Moo-Young goes to see his psychiatrist, Mo Jae-In. They begin their therapy session, and we’re taken back to when Moo-Young was representing Byeol’s mother in a wrongful death lawsuit they filed against the company Byeol’s father was working in. During the trial, Moo-Young was confronted by the company so much that he felt dizzy.
After the trial, Park Kyu advised Moo-Young to stop being too invested in his client’s cases as it was taking a toll on his health. Park Kyu also told Moo-Young to drop that case, which explains why Byeol’s mother was angry at Moo-Young earlier.
Back to the present, Lee Ro-Um’s prison mate, who was confronting her earlier over not helping with cleaning the cell, starts mistreating Lee Ro-Um. She tells Lee Ro-Um how much she despises people who disrespect their parents. She’s saying so because Lee Ro-Um allegedly killed her parents.
The next day in court, Moo-Young realizes Seo Gye-Sook isn’t at the spot where she was holding her sign yesterday. Woo Young-Ki comes and tells him about Seo Gye-Sook’s case. She gave her son, Myung-Hoon, up for adoption, although he was 18 years old. When Myung-Hoon died, Seo Gye-Sook discovered his adoptive parents had taken out severe life insurance policies against Myung-Hoon and were set to benefit from them now that Myung-Hoon is dead.
Later, news breaks out that the real person who killed Lee Ro-Um’s parents has been arrested. It turns out Lee Ro-Um was wrongfully arrested for her parents’ deaths and has been in prison for 10 years.
One of Moo-Young’s colleagues at Park & Cue Law Firm, Jo Jae-Hoon, is upset because Park Kyu has asked him to represent the actual criminal who murdered Lee Ro-Um’s parents. But, Moo-Young tells them that he will take on this case. So, Moo-Young takes on Lee Ro-Um’s murderer’s case while Jae-Hoon takes on Seo Gye-Sook’s case.
Moo-Young goes to talk to Lee Ro-Um’s parents’ alleged murderer, Ye Choong-Sik. Surprisingly, he admits to killing Lee Ro-Um’s parents and forcing Lee Ro-Um to set their house on fire with her parents’ bodies inside.
Moo-Young later asks Ryu Jae-Hyeok, who’s seemingly the prosecutor in Choong-Sik’s case, how many years he’ll push for Choong-Sik’s jail sentence. Jae-Hyeok calls out Moo-Young for being oversensitive with the cases he’s handling, a problem he is struggling with.
Moo-Young later tells his psychiatrist during his therapy session that he’s about to do something. The psychiatrist is against it and tells him what he’s about to do is career suicide.
It turns out what Moo-Young was talking about is his submission of a recording of Choong-Sik confessing to killing Lee Ro-Um’s parents to the media. Now everyone knows he killed Lee Ro-Um’s parents. Lee Ro-Um is finally released from prison but on probation. Moo-Young brings Lee Ro-Um new clothes to wear when she’s released.
Later, Park Kyu tells Moo-Young how much trouble he is in for betraying Choong-Sik, his client, and saving Lee Ro-Um. He then tells him that Lee Ro-Um now wants him to represent her in a defamation lawsuit she has filed.
Moo-Young later meets with Lee Ro-Um, and Lee Ro-Um begins opening up about how hard it has been for her when she was in prison. Later, as Moo-Young is with his psychiatrist again, he asks her how he can spot psychopaths. He then remembers seeing that something was off with Lee Ro-Um. Moo-Young then embarks on investigating Lee Ro-Um on his own.
He contacts Ms No, who was Lee Ro-Um’s former prison mate. She tells him how Lee Ro-Um stabbed a correctional officer because he told her to finish her food. He also contacts a correctional officer who worked at Lee Ro-Um’s prison.
He tells him how Lee Ro-Um threatened her prison mate (the one who confronted her earlier about not helping with cleaning) to put methanol in her eyes while she’s sleeping if she harasses her again. However, Lee Ro-Um was actually using water to threaten her and not methanol, as she earlier believed.
Lee Ro-Um reports to her probation officer, Go Yo-Han, who doesn’t look like the typical probation officer you’d expect to see. While this is going on, Moo-Young is still trying to figure out who Lee Ro-Um is. He calls the studio where Lee Ro-Um is currently staying and finds out she has left her studio.
Well, Lee Ro-Um isn’t as innocent as she appears to be. She heads to several jewellery and clothing stores, pretending to be a police officer, and dupes them into giving her clothes, handbags, shoes, and jewellery.
She then goes to a casino and uses her skills to win games of blackjack way more than the casino expected. The casino operators pay her off to stop playing, putting the casino’s profits at risk. She then pays a cyclist to return the trinkets she duped the owners into giving her.
Lee Ro-Um gets back to her studio and finds Yo-Han waiting for him. He begins asking questions about where she’s been and what’s inside the bag she’s carrying. As Yo-Han insists on seeing the contents of Lee Ro-Um’s bag, Moo-Young approaches and tells Yo-Han he has no right to check what’s inside. Inevitably, Yo-Han has no other choice but to leave.
The episode ends with Moo-Young opening Lee Ro-Um’s bag and money spilling out of it.
This show is off to an interesting start. There’s Moo-Young, a lawyer who seems overly sympathetic to his clients. Then there’s Lee Ro-Um, who may have been wrongly accused of killing her parents but has a criminal side that she’s hiding quite well.