Episode 4 of "The Frog" delves deeper into the past, as Sang-jun eagerly guides Eun-gyeong and Gi-ho through the Motel's corridors, their footsteps echoing through the halls before the fateful purchase. This nostalgic stroll echoes the haunting words of Sang-jun's late wife in her suicide note, a plea for tranquility, her ultimate escape. Amidst the sorrow, she tenderly whispers a message to Gi-ho, a testament to her unwavering love.
Sang-jun confronts Hyang-cheol behind bars, seeking answers for his own torment. He demands to know why he should suffer when Hyang-cheol's arrival has upended his world. Hyang-cheol retaliates, turning the tables by questioning Sang-jun's own actions that fateful night on the bridge. Before departing, he acknowledges Bo-min's assistance, grateful for one last glimpse of the killer.
Meanwhile, Bo-min harbors a secret agenda, her fascination with perilous murder cases simmering into an exhilarating obsession. She earns the moniker "It," as her captain likens her to a reckless player in a deadly game of tag, fueled by the adrenaline rush that she keeps carefully concealed.
In the present tense, Yeong-ha rushes to Seoul, his heart heavy with fear for his daughter Ui-seon's safety. Sung-a's shadowy presence lingers, and Yeong-ha's pursuit through the streets ends in frustration as he loses sight of her. His visit to Yong-chae is shrouded in secrecy, his suspicion that Sung-a is Si-hyeon's killer unspoken.
A year prior, Sung-a booked the Motel under Si-hyeon's name, a detail that gnaws at Yeong-ha's mind. The phone number provided is now defunct, adding to the mystery. Back at the Motel, Yeong-ha is consumed by a relentless quest to uncover Sung-a's secrets. And as the pieces slowly fall into place, it becomes clear that the key to her hidden agenda lies within the confines of her laptop.
However, Yeong-ha's attempts at discretion prove futile as he boldly carries the laptop to a computer repair shop, determined to unlock its secrets. The technician's solution, a stark reminder of the gravity of his actions, is to reformat the device—a drastic measure that would erase every trace of its contents, hardly the outcome he had envisioned.
On his return journey, Yeong-ha's attention is drawn to a procession of white trucks lumbering down the road, narrowly avoiding a collision but leaving behind a trail of mysterious plants scattered about the motel, a bizarre sight that doesn't escape his notice upon his arrival. Adding to the surreal atmosphere, the pool area reveals a grotesque display of torn art portraits, floating like abandoned whispers of a forgotten story.
Consumed by his suspicions, Yeong-ha delves deeper, snooping through Sung-a's car and uncovering evidence of her pharmacy visits. His discoveries culminate in a confrontation with Sung-a, fueled by anger and betrayal, after he learns of her hiring movers to dispose of his belongings. In a fit of rage, he drags her into the pool, submerging and choking her in a desperate attempt to uncover the truth.
Miraculously, Sung-a emerges from the ordeal, but her composure, once as impenetrable as ice, now shows cracks. Her passion for art serving as a veil, Yeong-ha's relentless interrogation finally brings them face-to-face over dinner, where he lays out his findings: dashcam footage of her solitary departure, bloodstains he's uncovered, and the telltale signs of a hastily cleaned crime scene. Yet, Sung-a dismisses his accusations with a scornful laugh, her confidence unshaken by his half-truths and the threat of exposure.
She taunts him with the knowledge that he's chosen silence over justice, and even hints at the possibility of his own complicity, a year-long secret that still shrouds them both in mystery. Undeterred, Sung-a declares her intention to continue along her path, daring Yeong-ha to either confront her directly or retreat, maintaining a cautious distance.
The dinner concludes with Yeong-ha's abrupt departure, but the tension between them simmers, ready to boil over at any moment. Yeong-ha's hand rests heavily on the recording of their conversation, a potent weapon in his arsenal, along with Sung-a's laptop, a digital keyhole into her world.
At the police station's doorstep, Yeong-ha hesitates, weighing the consequences of exposing the truth against the risk of implicating himself. As he turns the car around, Sung-a, seemingly driven by her own agenda, accelerates wildly, crashing into Yeong-ha's vehicle with a jarring impact, sending shockwaves through the already fragile balance of their existence.
