The premiere episode of "Nine Puzzles" unfolds with high school student Yoon I-na returning to her home, a place now shrouded in sorrow following the loss of her parents, leaving her solely with an uncle for kinship. The heavens opened up with a torrential downpour, casting an eerie darkness as the lights failed to illuminate the surroundings. Upon her arrival, the backyard door stood ajar, a grim omen that preceded the sight of a puzzle piece lying in a pool of blood. Her uncle's lifeless body came into view next, a fatal stab wound to the neck from an awl, a tool meant for sharpening, now turned into a weapon of death. The peculiar puzzle piece bore the image of a wolf disguised in a rabbit's costume.
Detective Kim Han-saem, a fresh recruit to the force, scrutinized the scene, noting I-na's unexpected lack of emotional display. Preliminary investigations pinpointed Yoon Dong-hoon, the former superintendent and I-na's uncle, as having breathed his last an hour prior, at the stroke of 9 PM. Han-saem's search unveiled another awl, this one hidden in I-na's art studio.
Chief Dong-su, a colleague and compatriot of Dong-hoon's, approached I-na with empathy during questioning. She confessed to a blackout of memories upon entering her home. Her journey began at 8 PM, exiting school and boarding the bus. She took the elongated route from the bus stop, arriving at her doorstep around 9 PM. Her next conscious moment was the housekeeper's voice calling her name, followed by the harrowing discovery of her uncle's corpse.
Han-saem harbored suspicions that I-na might be the perpetrator. Six months prior, she had purchased three awls, one of which, bearing her fingerprint, had been identified as the murder weapon. A thirteen-minute window between her arrival and dialing 911 further complicated matters. The absence of signs of forced entry or a struggle hinted that Dong-hoon knew his assailant. By opting for a shortcut from the bus stop, I-na could have gained an additional eight minutes—sufficient time, perhaps, to commit the crime.
During Han-saem's subsequent grilling, it emerged that I-na and Dong-hoon had been at odds over her dormitory situation. She conceded to the argument but steadfastly denied any disputes concerning inheritance, her frustration finally showing as he ridiculed her claimed memory loss.
She retreats to the sanctuary of her home, lying precisely where Dong-hoon's lifeless body was discovered. Her mind wanders, painting vivid images of her slaying Dong-hoon, her face adorned with macabre splashes of crimson as her lips curl into a sinister smile. The ensuing day, she presents Han-saem with the enigmatic puzzle piece, pondering whether he possesses the acumen to unravel the killer's identity.
A decade passes in the blink of an eye, revealing I-na as an enigmatic soul, seemingly oblivious to societal norms. The thrill of bungee jumping captivates her, drawing her perilously close to the abyss. Her playful antics with her therapist belie a deeper turmoil, haunted by recurring dreams of her uncle's gruesome murder—a crime she struggles to recall in its entirety. When confronted, she deflects with abrupt, insightful observations, donning a facade of toughness that belies her aversion to returning home. On her departure, a fellow physician extends an invitation to an exhibition, adding another layer to her complex life.
Han-saem, meanwhile, has transformed into a rebel without a cause. His body is now adorned with tattoos, his attire resembling that of a vagrant. His disregard for conventional wisdom borders on recklessness. As the decade-long anniversary of Dong-hoon's demise looms, his obsession with the case remains undiminished. He tracks down I-na's ex-dormitory mate, Mrs. Yeom, who has been in exile abroad, and intimidates her husband, a former convict, into revealing crucial information. Mrs. Yeom recalls a fateful night when I-na sought her out as an alibi, and mentions an awl that once resided in their shared dormitory.
In present times, I-na frequents Han-saem's precinct, teasing him mercilessly about his unkempt appearance. Elsewhere, the precinct chief and Dong-su, now promoted to commander, pay their respects at Dong-hoon's grave. The chief, a steadfast loyalist, has returned to honor his fallen compatriot. They empathize with I-na, finding Han-saem's lingering suspicions towards her absurd. Yet, Dong-su acknowledges Han-saem's unpredictability but commends his unwavering dedication.
I-na, too, is a police officer—a criminal profiler, to be precise. Confident among her peers, she is also somewhat forgetful, her quirks earning her mild teasing from superiors devoid of malice. The inheritance from her parents' once-thriving hospital has bestowed upon her wealth, but her true riches lie in her enigmatic spirit.
In her latest assignment, I-na is tasked with unraveling the brutal murder of a young boy, just ten years old. His sibling, a previously inconspicuous figure akin to a wallflower, abruptly pretends to suffer from memory loss, prompting I-na to scrutinize him intently. She devises a clever game, walking him through their shared recollections, and his defenses crumble, ultimately confessing to the heinous crime.
Back at the precinct, Choi San, a fresh recruit, expresses a keen interest in the perplexing Yoon case. After the day's duties conclude, the team leader, Yang Jeong-ho, Dong-su, and Han-saem unwind over drinks. Dong-su and Yang chastise Han-saem for allowing I-na to manipulate him, hinting at his strategic attempt to build a rapport so she might inadvertently reveal crucial details. Yang suspects I-na's motive stems from ensuring Han-saem remains deeply entrenched in Dong-hoon's unresolved case.
Later, Han-saem painstakingly retraces I-na's movements on the night of the murder, puzzled by her decision to take a longer route that lacks CCTV coverage, rendering her path unclear. Meanwhile, at 8:45 PM, a young woman at a bar feels an eerie gaze upon her; she glances over to find a man scrutinizing her intently.
Han-saem's detective instincts lead him to spy on Dong-hoon's residence, prompting the housekeeper to alert the authorities. It transpires that Han-saem's habit of lurking around has become a notorious trait among his peers, which they attribute to his lack of promotion.
At 9:32 PM, the bar-goer exits in a red car, accelerating recklessly and running a red light. Unnoticed by the officers busy at a nearby supermarket, she drives off unchallenged. By 10:07 PM, the red car arrives at The One City building, marking yet another significant timestamp in the investigation.
As Nine Puzzles Episode 1 draws to a close, I-na makes her way to Dong-hoon's house. The housekeeper is just about to leave when a delivery arrives—an enigmatic second piece of a puzzle depicting a serpentine woman conversing with a girl. Panicked, I-na hastily dials Han-saem's number, but her call falls on deaf ears, leaving her to confront the latest twist in this intricate saga alone.
