As the third episode of Pro Bono unfurls, Da-wit is shocked to discover that the notorious conman Jae-beom has been making inquiries at his office, prompting him to fear that his PA, I-na, may be an accomplice. He dispatches a spy to keep an eye on her.
Back to the Byeol case, the dog cafe owner is granted the right to keep her beloved pet. Gi-ppeum's heart flutters with excitement as Da-wit declares his commitment to defend the defendants. A flashback reveals that Gi-ppeum is a self-proclaimed nerd, with a passion for movies and an obsession that sets her heart racing. Her decision to become a lawyer stemmed from a memorable family court victory.
However, Gi-ppeum is given a reality check when Da-wit returns to his snobbish self, shunning pro bono cases in favor of "classy" ones involving wealthy corporations. He engages in heated debates with both Gi-ppeum and Nan-hui, who sees him as selfish while Da-wit perceives her as an entitled rich kid who hasn't experienced real suffering.
Determined to show him the value of the team's work, Gi-ppeum promotes them at a queer festival by dressing Da-wit in drag and taking him to a low-scale labor union conference. Jang Yeong-sil, the skilled pro bono lawyer, manages to secure a reporter through a contact. Meanwhile, Jung-in is being interviewed for her contributions to the firm's diversity efforts and ropes in Da-wit, who delivers his usual spiel about looking out for the common man. He finds it odd that Jung-in hasn't conducted a background check on him before hiring him.
A new case presents itself for the pro bono team: a young, disabled boy who wants to sue God for his paralyzed legs. The ambitious Jun-u sides with Da-wit, but the rest of the team wants to take up the case. Da-wit begins to soften when Gang-hun, the boy, wishes he had never been born. That night, Da-wit sees his taxi driver, who is deaf but doing his best, and is further moved.
Over the next few days, Gang-hun follows Da-wit around, trying to convince him. The pro bono team is amused by Da-wit's playful demeanor. One day, Gang-hun's mother, So-min, finds him and slaps him for going off on his own. The team is shocked, but Gang-hun doesn't blame his mother who has depression and was an orphaned teen when she had him. She believes she is being punished and Gang-hun is hurt that she sees him as her punishment.
However, a rift emerges between Gi-ppeum and Da-wit, as the latter refuses to offer Gang-hun false hope by taking on a seemingly lost cause. He perceives Gi-ppeum's actions as purely theatrical, and flashbacks reveal that her former colleagues shared this sentiment. This is why she leaves her old division and joins the pro bono team, under the encouragement of Yeong-sil.
With renewed determination, Gi-ppeum embarks on the case, and Da-wit joins forces once she crafts a more plausible complaint—suing Woongsan General Hospital, the institution where Gang-hun was born. We learn that So-min was indulging in alcohol and drugs, which may have contributed to Gang-hun's disability. Moreover, it was an unplanned pregnancy; she desired an abortion but the hospital delayed until it was too late for her to terminate it.
As expected, Myeong-hun steps forward as the hospital's counsel. Judge Kim, presiding over the trial, is blind but impartial, ensuring she cannot be accused of bias. Through the arguments of both parties, it becomes clear that CEO Choi Woong-san and his hospital are pro-life. So-min begins to attend the hearings, eager to make amends for her son. Da-wit nearly swayed the judge by highlighting that the hospital should have informed So-min about the fetus's malformation.
However, Judge Kim declares that the hospital's negligence did not cause Gang-hun's paralysis. Furthermore, she reminds us that all lives are equal, and thus, she cannot declare that Gang-hun's birth was damaging. The case is dismissed.
To lift everyone's spirits, Gi-ppeum treats them at her family's bakery. Her parents are deaf, and her father, who was scammed, now drives a taxi and runs a small bakery to provide for them. Da-wit feels remorse for his assumptions about Gi-ppeum's background.
Soon, Gang-hun's case is taken to the appellate court. Da-wit appeals by announcing his intention to sue CEO Choi Woong-san, asserting that if all lives are equal, he must prove that his hospital treats every life equally.
In the epilogue, Gi-ppeum's father stands trial. The judge declares him exempt from his debt due to his being scammed. And that judge is none other than Da-wit! He is the reason Gi-ppeum became a lawyer in the first place. The father cannot hear the verdict, so Da-wit signs that he has won, symbolizing a new beginning for both of them.
