Episode 1 of Season 1 of "The Defects" begins with a nostalgic flashback to the year 2011. The narrative introduces us to two figures, their silhouettes sharp against the backdrop of a decrepit warehouse as they navigate their way inside. One of the men, his voice laden with intrigue, tasks Tae-sik with handling a delicate matter, promising him a handsome reward. He teases Tae-sik with curiosity about the nature of the job, but Tae-sik remains steadfast in his resolve, stating that he doesn't want to know; his only concern is to settle his mother's mounting hospital bills.
Moments later, Tae-sik is seen struggling with a bulky black bag, heaving it into a colossal metal container. Just as he's about to pour in a mixture of cement, the bag stirs with unexpected life. When he unzips the bag, Tae-sik is stunned to find a young girl staring back at him, her eyes pleading for mercy. With a trembling hand, he draws his gun and pulls the trigger.
Cut to the present, where a young woman navigates the bustling downtown, her destination a dilapidated bathhouse. Inside, she prepares noodles for her younger siblings, four children who now call this clandestine sanctuary their home. Surveillance cameras blanket the premises, and a police scanner crackles in the background. Among the kids, So-mi pouts, longing for chicken instead of the humble noodles on offer. To lift her spirits, A-hyeon vows to procure the desired feast.
The children slip out of the bathhouse unnoticed, their movements instantly pinging on Tae-sik's phone as he tracks them with meticulous precision. Desperate for funds to fulfill So-mi's wish, the kids infiltrate an underground gambling den. Chaos ensues as they clash with the guards, while So-mi and Joo-an expertly crack open the safe.
After a fierce battle, the kids emerge victorious but content themselves with just enough money to buy chicken. They slip away just as the police sirens begin to wail in the distance.
With their cherished meal in hand, the kids receive a message from Tae-sik, inquiring about their whereabouts. They scurry back to their hideout, where Tae-sik awaits, ready to train them. As bullets fly towards their targets, each child is transported back to the moment their adoptive parents betrayed them. They envision taking justice into their own hands, pulling the trigger on the figures who once called themselves parents. Their recollections paint a picture of immense suffering at the hands of these supposed caregivers. Later, Tae-sik issues a stern warning, cautioning them never to venture outside again if they value their lives.
So-mi unleashes her fury upon Tae-sik, casting him as the scapegoat for their bleak existence. Nevertheless, A-hyeon gently reminds her that they all yearned for survival, highlighting that Tae-sik had been their saviour. In a subsequent conversation with A-hyeon, Tae-sik unveils his strategy for the children's future. He envisions sending them beyond the borders of Korea, where they can embark on a fresh chapter. He has already arranged for a modest vessel to spirit the kids away in the near future, urging A-hyeon to await his call with patience. Tae-sik vows to reunite with them once he ties up a few loose ends.
The following day, Tae-sik approaches his supervisor, seeking opportunities for business expansion. He proposes bypassing Director Jung and directly courting higher authorities for potential growth. His boss, however, declines, warning of the inherent dangers and the unknown entities these higher-ups might represent.
Elsewhere, Se-hee, a compassionate woman, visits a children's home, sharing a meal filled with warmth and camaraderie with the residents. Meanwhile, in a stark contrast, Jung-hyeon eliminates a reporter who had been onto their illicit child trafficking activities. Concurrently, A-hyeon finds herself revisiting old footage of Se-hee, a parenting expert, offering sage advice on nurturing affection in families.
The narrative shifts to Se-hee at her daughter's school, where she beams with pride at her daughter's academic strides. Conversely, another mother, Min-joo, is dissatisfied with her son Si-woo's progress. The teacher informs Min-joo that Si-woo is not a mathematical prodigy and unlikely to gain admission into the prestigious Mensa maths class.
Min-joo, crestfallen, resolves to return Si-woo. As a call intended for Se-hee rings out, she subtly disconnects it, shielding her daughter from any potential disturbances. Se-hee subtly exploits her daughter's presence to gather more insights about Si-woo. Meanwhile, in another part of town, Tae-sik's boss tasks him with handling Si-woo's refund, leaving behind Min-joo's voice recording for Tae-sik's perusal before departing.
Si-woo, innocent and unaware, pleadingly asks his mother to accompany him for some playtime, little does he know she is secretly orchestrating his untimely demise. Min-joo, with a cold resolve, dials her husband and persuades him that abandoning Si-woo is their only recourse, urging him to feign concern once their son goes missing. As if rehearsed, Min-joo stands by patiently, awaiting Si-woo's abduction, before embarking on her charade of a distressed mother searching for her lost child.
Tae-sik, burdened with the grave task, whisks Si-woo away and plays him the chilling recording of his mother's call to their handlers. He vows to shield Si-woo and breaks the heart-wrenching news of his parents' betrayal to the eleven-year-old. Just as his boss calls to ascertain the progress, Tae-sik finds himself pressed for time. In a hurried decision, he deposits Si-woo near the bathhouse, instructing him meticulously on his next steps.
Fatefully, Si-woo spots a payphone and dials his mother’s number. Despite initial skepticism towards Tae-sik’s revelations, the chilling indifference in his parents' response to his plea shatters him. Tears stream down his face as the harsh reality sets in – Tae-sik's words were all too true. Simultaneously, Tae-sik texts A-hyeon, alerting her of Si-woo’s safe arrival.
Alerted by Si-woo’s call, his parents frantically contact their superiors, seeking clarification. Jung-hyeon, suspicious, rings Tae-sik’s boss and demands Si-woo’s whereabouts. The boss speeds to the warehouse, only to find Tae-sik wrapping up his duties with a pretense of calm. Tae-sik feigns Si-woo already being disposed of, but Jung-hyeon’s timely arrival complicates matters. In a swift motion, Jung-hyeon eliminates Tae-sik’s boss and demands proof of Si-woo’s demise. Tae-sik seizes Jung-hyeon’s gun, igniting a fierce gun battle. Amidst the chaos, Tae-sik narrowly escapes, though Jung-hyeon and his men remain in relentless pursuit.
A high-speed chase ensues, with Jung-hyeon relentlessly attempting to force Tae-sik’s car off the road. Meanwhile, at the bathhouse, Si-woo arrives safely, greeted by the warm embrace of his newfound friends. They endeavor to lift his spirits, but Si-woo’s tears flow uninterrupted. Over the radio waves, news of his disappearance reaches their ears. Concerned, they inquire if Si-woo has reached out to anyone, to which he confessionally admits calling his mother.
A-hyeon, sensing Tae-sik’s peril, rushes to his aid but arrives too late to avert disaster. She stands frozen in horror as Jung-hyeon succeeds in pushing Tae-sik’s car off the road, which somersaults several times before bursting into flames.
The epilogue flashes back to the night Tae-sik rescued A-hyeon, when she gifted him a handkerchief adorned with her name tag. Later, he led her to the abandoned bathhouse, which A-hyeon promptly declared her new home. Soon, Tae-sik brought more children, and they forged a family bond, sharing meals, taking photographs, and living like a genuine family, united in adversity and hope.
