Years ago, a teenage girl set off on a bus journey with her friend, but their trip quickly veered off-course. Suddenly, a toxic gas filled the air, leaving everyone on board unconscious. When she finally regained consciousness, she found herself on a stretcher in an unfamiliar place, surrounded by the mysterious Dr. Baek and her twin. The doctor disclosed that the bus incident was a cover-up for something far more significant — the girl’s unexpected pregnancy held a secret that would gradually reveal itself, presenting both awe-inspiring and dangerous challenges.
Fast forward to the present day, where a tenacious girl, known as Ark 1, makes a daring escape from the grips of a secret laboratory, having dispatched her captors with startling ferocity. Disoriented and isolated in the woods, she is haunted by the fading echoes of her mother’s gentle voice. Her journey takes a darker turn when she is captured by Yong-Doo's men, who are fated to transport another hostage, Kyung-Hee, a woman fiercely determined to safeguard her inheritance from the vicious gangster.
As Ark 1 bravely navigates this treacherous terrain, her very existence sets off a series of explosive events, leading to a thrilling car chase. Kyung-Hee's quick wit and ingenuity prompt her to enlist the help of her uncle, a proficient surgeon who performs a crucial emergency operation to remove the experimental devices embedded within Ark 1’s skin.
In the meantime, Dr. Baek receives a menacing visit from Jang, the shadowy leader of the secret institute, who dispatches operatives to capture the escaped girl at a coastal base on Jeju Island. As night descends, Yong-Doo and his henchmen impose a wicked toll on Kyung-Hee, coercing her to relinquish her father's property — a shocking twist that unveils a long-hidden tragedy. Sensing imminent danger, Ark 1 intervenes with unyielding ferocity, sending the henchmen fleeing in chaos. In a strategic response, an agent named Jo-Hyeon, along with her loyal ally, Tom, consults with Dr. Baek, who offers them a device capable of tracking the elusive Ark 1. The stakes rise as Yong-Doo unleashes his fury upon Kyung-Hee's uncle, desperate to uncover information about the enigmatic girl.
As Kyung-Hee resumes her bustling market endeavors with her uncle’s injured figure, a sudden epiphany nudges her towards action. Upon returning to their vehicle, she encounters Jo-Hyeon and Tom, who display shocking footage of the menacing Ark 1 ruthlessly dispatching those surrounding her before her daring escape. They implore her to ally with them to prevent this rogue individual from committing further horrors, igniting a chain of events that will forever change their lives.
Meanwhile, Yong-Doo's clandestine conference with Jang's merciless team results in unexpected gains for him — he gains extraordinary powers in exchange for revealing Ark 1's location. As Kyung-Hee heads home with directives to flee with her brother once fireworks erupt, the air thickens with anticipation as Yong-Doo and his crew approach.
In a poignant act of bravery, Kyung-Hee sacrifices herself to provide a crucial distraction for Dae-Gil and Ark 1's escape, succumbing to a grievous wound amidst the turmoil. Jo-Hyeon’s tactical unit launches a bazooka assault aimed at neutralizing the lethal girl perched atop a rooftop, but Ark 1 miraculously dodges their onslaught.
Though Dae-Gil narrowly escapes the destruction of their home, tragedy strikes as he faces a grim fate at Yong-Doo's hands while witnessing his sister’s lifeless body. Following this disaster, Jo-Hyeon and Tom are decimated by Jang's crew before Ark 1 exacts her revenge upon them. Despite having acquired superhuman abilities through mysterious means, Yong-Doo is left incapacitated, his broken feet rendering him powerless against Ark 1’s rampage.
As the remnants of the tactical team meet their doom at her hands, Goo Ja-yoon arrives at the scene in a vehicle, finishing off the last survivor and revealing to Ark 1 that they share a familial bond. With their connection solidified, Ja-yoon seeks her sister's help in locating their mother, whose psychic connection with Ark 1 is intensifying.
Remaining resolute, Ark 1 stays fixated on her grief over the loss of Dae-Gil and Kyung-Hee, even as Yong-Doo succumbs to his injuries. Once Ja-yoon administers a tranquilizer to Ark 1, she is subdued and swept away in a vehicle alongside her sister.
As the film reaches its conclusion, Dr. Baek senses an impending threat to the sisters as they reunite. Yet, a shred of hope emerges when their mother is momentarily seen within a gigantic aquarium, wires snaking through her body. With a flutter of her eyes, she awakens as the screen fades to black.
In a post-credits moment, Jo-Hyeon and Tom reemerge alive, assembling with a group of "witches" as they gear up to hunt down Ja-yoon and her sister.
