In 2024, political and territorial tensions among China, Japan, and South Korea push the region toward instability as Japan reasserts its military presence and the United States and Russia jockey for influence in East Asia. Against this backdrop, the North and South Koreas decide to pursue reunification within five years as a means of survival, hoping to weather the mounting external pressure. Yet this bold move triggers a cascade of economic shocks: the main powers levy steep tariffs on the Koreas, sparking a severe recession that erodes public support for reunification and fuels widespread unrest. Civil strife, rising crime, and terrorist incidents multiply as anti-reunification factions take hold, culminating in the emergence of a domestic terrorist cell simply known as the Sect. To counter the escalating threat, the South Korean government expands the National Police Agency’s reach and creates a formidable Special Unit, outfitting its soldiers with futuristic powered exoskeletons and distinctive gas masks with glowing red lenses that become a symbol of the unit’s fearsome capabilities. This force proves capable of suppressing the Sect, but a year after its formation, a tragedy known as “Bloody Friday” changes everything: during a raid, a Special Unit team mistakes young schoolgirls for Sect terrorists and 15 of them are killed. The public backlash is so intense that the unit now deploys with its gas masks on to protect the identities of its members, while tensions with the Public Security Department—an internal intelligence arm that wants the Special Unit dissolved—grow hotter.
By 2029, tensions erupt again when an anti-reunification protest at Gwanghwamun Plaza in Seoul turns violent as Sect terrorists assault riot police with firearms and charges, killing officers and bystanders alike. The Special Unit is dispatched to crush the assault and raids the Sect’s hideout in the storm sewers beneath the city, eliminating most of the militants who refuse to surrender. In the heat of battle, Lim Joong-kyung Gang Dong-won confronts Lee Jae-hee, a young Sect courier carrying a satchel charge; she detonates the device, sacrificing herself and leaving Lim shaken but resolute. The incident stains the unit’s reputation, and Lim is pulled back for reevaluation under drill instructor Jang Jin-tae Jung Woo-sung.
The narrative deepens when Han Sang-woo, the head of Public Security, informs Lim that the deceased courier has a sister—Lee Yun-hee Han Hyo-joo. Lim meets Yun-hee at Namsan Tower, where she reveals she does not condemn Lim for the death, as they were fighting on opposite sides. Behind Yun-hee’s calm façade, however, lies a more complicated truth: she is a former Sect courier who has been reluctantly drawn into Public Security’s plan to delegitimize the Special Unit in exchange for a chance at a medical operation for her ailing brother. Underground forces within the government, an internal deep-cover faction known as Illang, are secretly trying to protect Lim and his team from Public Security’s manipulation.
In a tense turn of events, Yun-hee is captured and interrogated by Kim Cheol-jin [Minho], a member of Illang, who uncovers that the Sect’s finances are tied to Public Security and that Yun-hee had been coerced into killing for them. After her release, Yun-hee heads to the site of Public Security’s trap at Namsan Tower with a tracking device to expose Lim, but Lim senses the trap, kills the trapped agents, and escapes with Yun-hee. He then passes along photographic evidence of Han’s involvement with the Sect to Han Sang-woo, igniting a nationwide manhunt for the two.
Illang arrives on the scene, providing Lim with a powered exoskeleton and a machine gun to confront the imminent threat, and safely extracts Seo-hee Shin Eun-soo—the previously undercover ally who is revealed to be Kim Seo-hee, the Sect’s former commander—so she can be safeguarded. The Public Security squads and Han converge on the location of Yun-hee’s tracking beacon, only to be met by a fully equipped Lim, who decimates the opposing forces in a drawn-out, brutal firefight.
As the dust settles, Lim reunites with Seo-hee and the Illang team, but a moral dilemma erupts: Jang Jin-tae orders Lim to execute Seo-hee as a perpetual terrorist who spied for Public Security. Lim refuses, choosing mercy over betrayal; Jang allows Seo-hee to live and resumes the battle, ultimately accepting Lim’s decision to retire from the Special Unit. In a quiet close to the chaos, Seo-hee and her brother board a train out of Seoul; as the train chugs away, Seo-hee peers out the window and catches a final, lingering glimpse of Lim, signaling a complex, unresolved bond that lingers beyond the immediate conflict.
