After Japan's surrender at the end of World War II, the People's Liberation Army faces the daunting task of reclaiming territories that have been overrun by bandits who seized Japanese arsenals. At the forefront is Shao Jianbo, known as Captain 203, who commands a ragtag group of 30 men. With supplies critically low, the dire situation takes a turn for the better when they defeat a gang of bandits disguised as PLA soldiers guarding vital ammunition stores.
Hope arrives in the form of reinforcements aboard a train: Yang Zirong and Bai Ru, a highly skilled combat medic. Their timely arrival brings not just much-needed food, but also renewed morale. Captain 203 leads his men to a village that has fallen victim to bandit raids. While traversing the perilous journey, they encounter a young boy grieving the loss of his family due to the bandit onslaught. Initially wary of the PLA soldiers, the boy's feelings shift as they bravely rescue him from a bandit spy lurking in the village.
The villagers, desperate for protection, urge the soldiers to remain and confront the malevolent warlord Hawk, fearing he will continue his predatory raids once the PLA departs. By interrogating the captured bandit spy, Captain 203 learns that Hawk is on the hunt for a map meant to guide him into a valuable territory. Given their overwhelming disadvantage in numbers and firepower—Hawk's bandits are fortified in a formidable fortress atop Tiger Mountain—Zirong volunteers to act as a spy to penetrate the enemy’s ranks, citing his past successes infiltrating local bandit groups. Although Captain 203 is initially resistant, he ultimately acquiesces following Zirong's earnest resignation.
Zirong smartly acquires the spy's map and establishes a covert system to relay intel to his fellow soldiers. Throughout his precarious mission, suspicions swirl among the bandits, yet they reluctantly accept Zirong after he demonstrates his capabilities. A pivotal moment arises when Hawk sends Ma Qinglian, a woman abducted from the village and coerced into marriage, to test Zirong's loyalty. Recognizing her as the village boy's mother, Zirong discreetly assures her that her child is unharmed. Despite her pleas to flee back to safety, Zirong insists on remaining undercover to gather critical information.
As circumstances become increasingly perilous, Zirong evades exposure by ingeniously marking new locations for his intelligence reports when the bandits jeopardize his previous drops. Tensions escalate when Qinglian's longing for escape is overheard by Brother 2. Seizing the opportunity, Zirong slyly plants accusations of treachery on Brother 2, convincing Hawk to execute him, further sowing discord within the ranks of the bandits. Subsequently, a massive raid is launched against the village, with 300 bandits mobilizing for an assault. Thanks to Zirong’s timely warning, Captain 203 and his soldiers ingeniously set traps and employ makeshift artillery to defend against the overwhelming force, claiming several valiant soldier lives in the process.
The conflict intensifies when the bandit spy, previously captured, returns to the fortress, spurring accusations and chaos among the bandits. Hawk is initially incredulous that a small unit could defy his substantial forces, but he ultimately aligns with Zirong after being deceived by the bandit spy. During Hawk’s birthday feast, Zirong transmits an attack strategy, prompting Captain 203 to rally his troops. Guided by Qinglian's son to a vulnerability in the fortress, they proceed while Zirong orchestrates their success from the inside.
The climactic showdown unfolds when Hawk, in a desperate bid for survival, abducts Qinglian and escapes. Zirong pursues fiercely, concluding the confrontation in a dramatic gunfight that results in Hawk’s demise and facilitates a heartfelt reunion between Qinglian and her son. In a poignant epilogue set in the modern era, a descendant of Qinglian pays tribute to the courageous acts of Zirong and his brave comrades, including a fantastical depiction of Zirong engaged in an intense battle against Hawk, featuring an out-of-control airplane hidden within the fortress walls.
