In the fourth installment of "Family Matters," titled "The Good Samaritan," the Kim family's journey continues to unfold with a blend of nostalgia, suspense, and emotional depth. The episode begins by delving into the past, showcasing the training days of Young-soo and Chul-hee. From a young age, Chul-hee's unwavering dedication to protecting Young-soo is evident, setting the foundation for their strong bond. This flashback is juxtaposed with another from two years ago, where Chul-hee's recurring nightmares cause Young-soo to worry. Her fears, however, are not just about the past; she is also haunted by the possibility of losing her children, recalling a traumatic incident when Ji-woo went missing at an amusement park.
The narrative picks up from the previous episode's cliffhanger, where Young-soo uses her powers to torment No-won, making him believe he has suffered severe injuries. This act of retribution is witnessed by No-won's secretary and her father, providing them a sense of closure and relief. Meanwhile, Chul-hee's prowess is on full display as he single-handedly defeats Deacon Joe and his men. His training of Ji-hoon pays off, as they work together seamlessly to save Ji-hoon and Min-jung, highlighting the family's growing unity and strength.
Upon returning home, the family shares a warm dinner, with Grandpa and Ji-woo welcoming them back. However, Ho-chul watches from afar, feeling disappointed that his plans have been thwarted. Later, Young-soo expresses her gratitude to Chul-hee for his role in the rescue, and he reveals his motivation for helping No-won's secretary, drawing parallels to their own past.
The next morning, Young-soo and the children share breakfast, and Ji-woo brings up a conversation she overheard between her mother and Chul-hee. Young-soo reaffirms her promise to protect her children and mentions her intention to deal with Ho-chul. Ji-woo's mention of Ho-chul is supported by Grandpa, and Gang-sung suggests that catching Ho-chul as a family will further strengthen their bond.
Elsewhere, No-won returns home to his wife, Sister Oh, who is shocked by his condition. Meanwhile, the police arrest Dong-min, but Detectives Jung-hwan and Joong-man remain skeptical about his involvement in the serial killings. Despite the police chief's insistence on closing the case, Jung-hwan continues his investigation, leading him back to the vet shop.
Chul-hee's attempts to gift Young-soo a hairpin are interrupted, and he feels a pang of jealousy when he sees her wearing lipstick before leaving. Grandpa teases him about his past affairs, adding a touch of humor to the situation. Young-soo then confronts Pastor Yoon about the misconduct of officials in his church, and he is taken aback when she suggests that the serial killer might be a church member.
At home, Ji-hoon inquires about Young-soo's emotional state during her hypnotic rituals, and she explains that the pain she inflicts is also felt by her. This revelation deepens Ji-hoon's understanding of his mother's sacrifices. At school, the children celebrate their newfound freedom with Kyu-tae gone, while Jae-gon begins plotting his return to power. Pastor Yoon's visit to No-won and Sister Oh leads to a shocking turn of events. He informs Sister Oh about Young-soo's involvement in No-won's suffering, and she ultimately kills No-won, deciding that his life insurance is a better option than caring for him in his current state.
In the evening, Jung-hwan visits the vet shop and encounters Chul-hee, while Ho-chul drops by, leading to a confrontation. The fight escalates as Ho-chul pulls out a knife, and Grandpa intervenes. During the chaos, Jung-hwan discovers the family's connection to the car incident involving the victim's body. The episode concludes with the family returning home, finding the ongoing commotion and reflecting on their actions.
A flashback reveals that Young-soo and Chul-hee returned to the town to find the serial killer, a mission driven by the realization that the killer has followed them to every city they have lived in. The episode ends on a note of introspection, as the family grapples with their roles in the unfolding drama and their responsibility to protect each other and the community.