Episode 6 of *Queen Mantis* opens with the police meticulously analyzing the crime scene. Min-jae lies lifeless, and Su-yeol is racked with guilt. In a moment of profound resolve, he agrees to think and act like I-shin in exchange for her unwavering support. She is elated, sensing that her son is finally embracing her presence, albeit in such unconventional circumstances.
Meanwhile, Jeong-ho finds solace in the comforting embrace of his wife. He is plagued by doubts, questioning whether he is doing the right thing by aiding I-shin. She advises him to keep his emotions at bay and not to complicate matters with sentimentality.
During the subsequent call with the copycat, I-shin taunts him for his haphazard handling of Min-jae's murder. Determined to prove his prowess, the copycat initiates a video call, revealing his preparations for the fourth copycat killing. His setup is sloppy, and Ji-an quickly identifies the hotel. As the police race to the scene, I-shin is tasked with stalling the murder.
Upon arrival, the police are faced with the daunting task of searching ten floors. Na-hee is desperate to save the victim and suggests ringing the alarm to catch the copycat as he attempts to flee. Su-yeol, however, vehemently refuses, fearing it will alert the killer and potentially lead to the victim's demise, even if it means sacrificing the chance to save a life.
The search is painstakingly slow as they comb through each floor and every room. Suddenly, Su-yeol recalls a crucial detail from I-shin's fourth murder—Room 418. Their luck changes when they discover that the CCTV on the fourth floor has been disabled, hinting at the copycat's location.
Yet, as the copycat is on the verge of killing his victim, Na-hee, unable to bear it any longer, pulls the alarm in a desperate bid to save him. The killer, disguised as a guest, manages to slip away unnoticed.
Sung-gyu is taken aback by Su-yeol's refusal to agree to the alarm, especially considering his previous efforts to save victims at all costs. Na-hee's suspicion grows, and she urges Sung-gyu to delve deeper into Su-yeol's motives. She wonders why Su-yeol was so desperate to save Min-jae and why he has taken charge of their case with such fervor.
Later, a custody evaluation is scheduled for Na-hee’s autistic son. As the evaluation unfolds, Na-hee braces herself, her heart pounding with a mix of apprehension and hope. The boy, with a courageous glint in his eye, reveals that his father has always been there for him, a statement that resonates deeply with Na-hee. Meanwhile, Su-yeol is consumed by regret, haunted by the thought that she had allowed herself to think like I-shin and, in doing so, had placed the victim, Manager Son, in grave danger. But Su-yeol remains undeterred, her resolve unshaken, and she resumes the consultation with unwavering focus.
During a video call, a chilling revelation unfolds: the copycat is singing I-shin’s song, a tune that is unknown to all and absent from any records. The eerie melody sends shivers down the spines of those present. I-shin, in a moment of candidness, reveals that there are two wounds on her fourth victim, Kang Yeong-ho, that she did not inflict. They are shallow, almost as if made by a child.
Su-yeol’s mind races back to Kang’s son, Yeon-joong, a boy whose nose had been burnt off due to severe abuse. She recalls the stories of Yeon-joong roaming around with dead animals he had killed, calling out to her as if she were his mother. A flashback ensues, painting a harrowing picture: Yeon-joong, hidden in the shadows, watches with a gleeful grin as I-shin sings and takes his father’s life.
The police launch a frantic search for Yeon-joong, but it’s as if he has vanished into thin air. Jeong-ho, burdened by guilt, laments his failure to protect Yeon-joong from his abusive father. Elsewhere, Sung-gyu and Hyuk delve into Manager Son’s past, questioning his friend. They uncover a shocking truth: Son had hooked up with Jo-i and was left terrified when she urged him to kill her.
Meanwhile, Na-hee and Su-yeol pay a visit to Yeon-joong’s mother, who is now suffering from dementia. In a fragmented conversation, she reveals that Yeon-joong, now dressed as a woman, has just left. Her nurse corroborates the story, but their CCTV system is malfunctioning, leaving no trace of Yeon-joong’s whereabouts.
The police piece together the clues, deducing that Yeon-joong, now known as Jo-i, is not a catfish but a transwoman. They begin scouring clinics and medical records in a desperate bid to find her. As their attention is diverted, Sung-gyu takes the opportunity to snoop around Min-jae’s place, where he stumbles upon a revealing photo.
Su-yeol, on a different trail, tracks down a nurse who has encountered Jo-i. The nurse’s account is unforgettable; while other patients finally felt like themselves, Jo-i was overjoyed at the realization that women are no longer seen as threats, her words echoing with a profound sense of liberation.
Su-yeol dashes back to the unit in a frantic rush, only to be met with a wall of confrontation. The photograph in question bears the images of Min-jae, I-shin, and Su-yeol himself. Sung-gyu's eyes harden with accusation as he declares that Su-yeol is just a chip off the old block, a replica of his own mother. Meanwhile, Na-hee's fury simmers to a boiling point, incensed by Su-yeol's repeated deceit. Jeong-ho attempts to interject, to mediate the escalating tension, but Na-hee cuts him off with a stark ultimatum: choose between Su-yeol and the unity of their unit.
That fateful night, under the cloak of darkness, Su-yeol musters the courage to bare his soul to Jung-yeon, revealing the truth about I-shin. The revelation is a whirlwind, leaving Jung-yeon reeling, her mind struggling to process the flood of information. She needs a moment, a breath, to gather her thoughts. Su-yeol, however, misinterprets her silence, his heart sinking as he assumes she is consumed by fear of him.
In a vulnerable display, he confesses his own terror—a fear that gnaws at his very soul. He is terrified of the darkness within himself, the possibility that I-shin's killer instinct might be etched into his very DNA. With a tremor in his voice, he admits his reluctance to have children, haunted by the thought of passing on such a malevolent trait. In a final, desperate declaration of love, he bids her farewell and exits, leaving behind a trail of unresolved emotions and shattered silence.
