The Mantis: Original Sin, Season 1 (2025) begins with the reemergence of a series of brutal murders that mimic the style of a notorious female serial killer, Jung Yi-shin, known as the "Mantis," who was imprisoned two decades ago for killing five men. The police are baffled by the new killings, which replicate the precise and chilling methods of the original crimes, prompting them to bring Jung Yi-shin out of prison to assist in the investigation.

Detective Cha Soo-yeol, the lead investigator assigned to the case, is revealed to be Jung Yi-shin's estranged son. He harbors deep resentment toward his mother due to her past and the impact it had on his life. Despite his personal feelings, he must collaborate with her to stop the copycat killer. Their tense and emotionally charged reunion sets the tone for the season, highlighting the complex mother-son dynamic that underpins the investigation.

Early in the season, the police team, led by Soo-yeol, reviews old case files and trial records related to Jung Yi-shin's original murders. They discover that the new killer has accessed confidential court documents rather than public news reports, indicating an insider or someone with privileged access. This realization narrows the suspect pool and raises the stakes for the investigation.

As the investigation progresses, Soo-yeol and Jung Yi-shin analyze the crime scenes and the modus operandi of the copycat killer. They note subtle differences and clues that suggest the new murderer is not merely imitating but also sending a message. Jung Yi-shin uses her deep knowledge of the original crimes to predict the killer's next moves, guiding the police team through a series of tense stakeouts and confrontations.

A pivotal sequence occurs when the team confronts a suspect named Tom, who becomes hysterical and threatens to expose sensitive information about the Mantis and her family. In a violent outburst, Jung Yi-shin attacks Tom, slamming his head against a table and choking him, demonstrating her dangerous and volatile nature. The chaos escalates as Tom attempts to escape, pulling out a homemade pistol. The police try to de-escalate the situation, but Tom experiences auditory hallucinations and a mental breakdown, complicating the standoff.

Detective Soo-yeol approaches Tom calmly, empathizing with his hallucinations and trying to disarm him peacefully. Just as Soo-yeol reaches for the gun, Tom suddenly points it unpredictably, creating a tense moment that nearly ends in tragedy. The police manage to subdue Tom without further violence, but the incident exposes the psychological toll the case is taking on everyone involved.

Throughout the season, flashbacks reveal Jung Yi-shin's past, including the circumstances that led to her imprisonment and the psychological evaluation she underwent. These scenes provide insight into her motivations and the dark symbolism behind her "Mantis" nickname, which references the female praying mantis's habit of devouring the male after mating. The flashbacks also explore Soo-yeol's childhood and the emotional scars left by his mother's crimes and absence.

As the investigation nears its climax, Soo-yeol and Jung Yi-shin uncover a conspiracy involving individuals within the police force and legal system who have been manipulating the case for their own ends. This revelation forces them to question whom they can trust and pushes them to take bold actions to expose the truth.

In the final episodes, the mother and son confront the copycat killer in a tense and violent showdown. The killer is revealed to have a personal vendetta linked to the original murders, seeking revenge and recognition. The confrontation involves a carefully planned trap, with Jung Yi-shin using her knowledge of the killer's psychology to anticipate their moves.

The season ends with Jung Yi-shin and Soo-yeol narrowly surviving the confrontation. The copycat killer is apprehended, but the resolution leaves lingering questions about justice, redemption, and the possibility of breaking free from the shadows of the past. Soo-yeol begins to reconcile with his mother, acknowledging the complexity of her character beyond her crimes.

This detailed chronological account covers the major plot points, character decisions, confrontations, and emotional developments that drive the story of The Mantis: Original Sin, Season 1.

At the end of The Mantis: Original Sin Season 1, Cha Soo-yeol, a police officer, and his mother Jung I-sin, the infamous serial killer known as the Mantis, confront the copycat killer who has been mimicking her murders. The case reaches a tense climax where mother and son must face their painful past and the truth behind the new killings. Ultimately, the copycat is caught, and Soo-yeol begins to reconcile with his mother, though their relationship remains complex and fraught with emotional scars.

The final episode of The Mantis: Original Sin unfolds with a gripping sequence of events that bring the central conflict to a head. The story begins with Cha Soo-yeol intensifying his investigation into the copycat murders that eerily replicate the brutal killings his mother, Jung I-sin, committed two decades earlier. Despite his deep-seated hatred for her, Soo-yeol reluctantly collaborates with Jung I-sin, who is still imprisoned, to gain insight into the killer's methods.

As the episode progresses, Soo-yeol and Jung I-sin piece together clues that lead them closer to the copycat's identity. The tension between mother and son is palpable; Soo-yeol struggles with his conflicting emotions--resentment, fear, and a reluctant dependence on his mother's dark expertise. Jung I-sin, cold and calculating, reveals details about her past crimes and her mindset, which helps Soo-yeol anticipate the copycat's next move.

The climax occurs in a suspenseful confrontation where Soo-yeol and Jung I-sin track down the copycat killer. The scene is charged with emotional intensity as Soo-yeol faces the embodiment of his mother's legacy of violence. The copycat is revealed to be someone deeply connected to the original crimes, adding layers to the narrative's exploration of trauma and vengeance.

In the final moments, the copycat is apprehended, ending the cycle of murders. Soo-yeol and Jung I-sin share a quiet, fraught exchange that hints at a tentative understanding but also acknowledges the irreparable damage between them. Soo-yeol's fate is to continue his work as a police officer, burdened but strengthened by the ordeal. Jung I-sin remains incarcerated, her role as the Mantis intact but now complicated by her cooperation and the shadow of her son's presence.

The ending scene closes on Soo-yeol walking away from the prison, a man changed by the confrontation with his mother and the darkness they both embody, leaving viewers with a lingering sense of unresolved tension and the complex nature of familial bonds entwined with crime.

The TV show "The Mantis: Original Sin," season 1 (2025), does not have publicly available information or confirmed details about a post-credits scene. None of the search results or official sources mention a post-credits or end-credit scene for this series.

If a post-credits scene exists, it has not been documented or widely reported as of now.

Jung I Sin, also known as the Mantis, is a female serial killer who brutally murdered five men two decades ago. She is the mother of Cha Soo-yeol, a police officer who has loathed her his entire life. When a copycat killer emerges, Soo-yeol enlists her help to catch the culprit, setting up a tense and complex mother-son dynamic central to the story.

Cha Soo-yeol is the son of Jung I Sin, the Mantis. He has hated his mother for years due to her past as a serial killer. Despite this, he must work with her when a new series of murders mimicking her style occur, creating a fraught and emotionally charged partnership.

Yoon Hee-jin is a brilliant but troubled forensic pathologist and the mother of Park Ji-won. Set 20 years before the original series, she investigates a series of deaths she believes are connected, which strains her relationship with her daughter. Her obsession with uncovering the truth leads her into dangerous territory that ultimately shapes the events of the original story.

Detective Choi Min-ho is a reluctant ally to Yoon Hee-jin. He harbors his own secrets and their relationship forms the emotional core of the series, portraying two broken individuals who find understanding in each other despite knowing they cannot be fully saved.

The hospital director, portrayed by Yoo Jae-myung, presents a benevolent façade but hides a far more sinister nature. His quiet menace adds tension to the series and plays a key role in the unfolding conspiracy that Yoon Hee-jin investigates.

The TV show The Mantis: Original Sin (2025) is not family friendly and is generally unsuitable for children or sensitive viewers due to its intense crime thriller content involving serial killings.

Potentially objectionable or upsetting aspects include:

• Graphic violence and murder scenes, as the story revolves around a serial killer and copycat killings.
• Psychological thriller elements with dark, intense themes that explore trauma, obsession, and complex family dynamics.
• Disturbing subject matter related to crime, death investigations, and the emotional toll on characters.
• Strong emotional tension and suspense that may be unsettling for sensitive viewers.

The series is a mystery-thriller with a mature tone, focusing on a cop working with his mother, a notorious female serial killer, which inherently involves mature and potentially distressing content.