Episode 1 of "Family Matters" kicks off with a nostalgic glimpse back to 1996, setting the scene at the Special Trainings Battalion. Here, a woman stands tall, addressing a cluster of youthful children with a voice that resonates authority. She informs them that their families have left them behind, vowing to become their motherly figure and sternly warning them against any notion of escape. Yet, amidst this solemn gathering, one young girl, marked with an X on her chest, appears fiercely determined to contradict her every word.
The scene shifts to the present, where a family is cruising down the road, the radio blaring with news about a menacing serial killer dubbed "The Doom-veloper," who remains at large. His grim tally has reached nine female victims, and he's issued a chilling threat of another impending murder. His target: women residing in special development zones, prompting the authorities in Gyeonggi-do to halt several development initiatives. Despite his terrifying reign of terror, The Doom-veloper has gained an unsettling following, making his capture an uphill battle for law enforcement.
The parents, seemingly unperturbed by the serial killer's reign, are primarily concerned with their children's conduct at their new school. Their past escapades hint at a rocky road ahead. Their grandfather leaps to their defense, painting a picture of youthful misadventures rather than deliberate misconduct. The mother, with a reassuring tone, encourages her offspring to bring any issues they face at school straight home, pledging her unwavering support.
As their conversation unfolds, a sudden jolt interrupts their journey – another vehicle swiftly cuts in front of them, resulting in a minor fender-bender. The tension in the air thickens, a harbinger of the intriguing family dynamics and challenges that lie ahead.
The following morning dawned, ushering in a duo of detectives eager to commence their duties. One was firmly convinced that the latest case involving a missing girl was intertwined with the shadowy figure known as the Doom-veloper. The victim's mother, fraught with worry, was certain that her daughter, Yu-jin, was ensnared in peril. Yu-jin had last been glimpsed on the Kumsu-ro trail, with a mysterious man trailing her steps like a specter. Her mother's instincts screamed that her daughter was in dire straits, yet the police hesitated, adhering to the arbitrary rule of the 24-hour mark before classifying it as a missing persons case.
Elsewhere, Ji-woo and Ji-hoon, two siblings, prepared for their school day amidst a household teeming with tension. Their mother, Young-soo, resorted to a tactical bribe—a sleek laptop—hoping to entice her son into keeping an eye on his sister and reporting back. She attempted the same maneuver with her daughter, but the latter cut her off mid-sentence, revealing a fractured bond between mother and daughter. Gang-sung, the grandfather, offered sage advice, urging Young-soo to confide in her children regarding their family's predicament. Cheol-hee, their father, also harbored concerns for his offspring, yet he elected to place trust in their resilience and redirected his focus towards opening his veterinary clinic. His day took an unexpected turn when a call from the real estate agent summoned him to assist with a problematic canine.
At school, Ji-hoon found himself at odds with the omnipresent bully, Kyu-tae, but this time, he retaliated with unexpected ferocity, sinking his teeth into one of Kyu-tae's minions. A female observer, silent and intrigued, pondered if Ji-hoon's reputation as a loser was deserved. Whispers suggested that his previous school expulsion stemmed from a near-fatal altercation with a bully.
Meanwhile, Ji-woo confronted Kyu-tae over a compromising photograph he'd snapped of her slumbering at her desk. Her request for deletion fell on deaf ears, and Ji-woo struggled to maintain composure, honoring her pledge to her parents. The class president stepped in, her intervention prompting Kyu-tae to backtrack and relent.
Returning to his abode, the local clergyman visits the veterinary clinic, accompanying his canine companion for a thorough examination. Troubled by the dog's sudden propensity for biting individuals, his concerns deepen when a phone call interrupts his visit, informing him that one of his congregants has vanished. In haste, he entrusts his pet's care to the veterinarian and rushes away.
In the meantime, Gang-sung acquaints himself with his new surroundings, conducting a meticulous survey of all CCTV surveillance cameras in the vicinity. Elsewhere, a police detective scours the Kumsu-ro trail and discovers alarming clues: bloodstains and shattered jewelry scattered along the path. He receives a call from his colleague, who reveals that Yu-jin, the missing woman, led a relatively solitary life, frequenting church services and spending time with her family.
The authorities grapple with uncertainty, unable to ascertain whether Yu-jin absconded, was abducted, or fell victim to foul play. One detective, however, remains steadfast in his conviction that Yu-jin is the tenth victim of the infamous Doom-veloper. He presents circumstantial evidence gathered from the trail to his superior, but his hypothesis falls on deaf ears. Undeterred, he persists in his investigation.
Concurrently, the church convenes to pray fervently for Yu-jin's safe return. Among the congregants is a real estate agent, who harbors ulterior motives for joining the church. She, along with two other businessmen, exploits the church's charitable donations to amass properties in the surrounding area. Oblivious to their deceit, the church believes their contributions are funding the construction of a grander sanctuary. One of these businessmen, a church deacon who owns a restaurant, anticipates that once the serial killer is apprehended, they can proceed with their schemes unimpeded.
A harrowing revelation unfolds: the new family in town is imprisoning the man who collided with them in one of their animal cages. Ironically, the real estate agent who orchestrated this plot is also a church member, further entangling the moral fabric of the community in deceit and duplicity.
They are not an ordinary family, and Kyu-tae is about to find out why he shouldn’t have messed with Ji-woo. Concurrently, Ji-hoon realises that Kwon Mi-jung is following him. She tells him that she is worried about Ji-woo since she went to meet Kyu-tae after school. Kyu-tae has been taking photos of girls and using AI to turn them into pornographic content. He then uses the pictures to threaten the girls to take more sexual content.
This time, he messed with the wrong girl because Ji-woo fights him and his bully friends. She breaks one of the bullies’ fingers and knocks out Kyu-tae. Ji-hoon arrives to find the bullies already taken care of. He advises Ji-woo to take Kyu-tae to their mom.
At home, Cheol-hee and Young-soo start to suspect that Pastor Yoon has been abusing his dog. They are surprised when their kids arrive with an unconscious Kyu-tae and explain why they brought him home. After hearing what Kyung-tae has been up to, the parents are pissed. Ji-woo convinces their mom to handle it like she kidnapped the rude man who crashed into their car and cursed at her.
The man is still locked in a cage, since they don’t know what to do with him just yet. Ji-hoon begs their mom to do her thing and finally show Ji-woo her capabilities.
Young-soo agrees and ties Kyu-tae to the examination table. She then proceeds to cut out a pound of his thigh. Cheol-hee and Gang-sung leave, but Ji-woo and Ji-hoon remain behind to watch. Cheol-hee admits to his dad that he is worried that Young-soo chose to return to this town.
Gang-sung harbors a tapestry of emotions regarding the town. Within the confines of the veterinarian's clinic, Young-soo persists in excising a fleshy fragment from Kyu-tae's thigh, after inscribing the word 'sin' upon it with an air of ceremony. Ji-woo's visage betrays a deep revulsion, whereas Ji-hoon appears oddly entertained by the spectacle of Kyu-tae's agony, relishing each moment of his suffering.
