In the year 2036, as a result of escalating tensions, a civil war erupts in Ukraine, prompting the United States to send peacekeeping troops to the volatile region. During a crucial operation, a battalion of Marines and their robotic counterparts known as Gumps fall into an unexpected ambush. Defying a direct command, 1st Lt. Harp (played by Damson Idris) employs a Hellfire missile in a drone strike against an alleged enemy launcher. This action, while saving 38 Marines, results in the tragic loss of two comrades. As a consequence, Harp is reassigned to Camp Nathaniel, the US's operational headquarters in Ukraine, where he meets Captain Leo, portrayed by Anthony Mackie. Unbeknownst to Harp, Leo is not just a military officer; he is, in fact, a highly classified and experimental android super-soldier pretending to be an eccentric human.
Harp and Leo embark on a critical mission aimed at thwarting the plans of the pro-Russian terrorist Victor Koval, who aims to seize control of a network of Cold War-era nuclear silos. Their cover story involves delivering vaccines to a refugee camp in dire need. As they make their way, their convoy responds to a distress call regarding an attack on a friendly humanitarian aid truck. This situation leads to a tense standoff between the US Marines and armed local citizens. A Gump unit escalates the tension by preemptively shooting a local who throws a rock, sparking a conflict. However, Captain Leo manages to negotiate peace, donating the contents of the aid truck to the locals. The moment of calm is shattered when pro-Russian insurgents ambush the Marines and the locals, igniting a fierce firefight. Consequently, Leo and a hesitant Harp are forced to trek to the refugee camp on foot, leaving the Marines to fend off the insurgents.
Upon their arrival at the refugee compound, they find themselves under fire from an insurgent sniper, leading to the tragic killing of several civilians while they narrowly escape injury. The situation escalates when Harp witnesses Leo employ brutal interrogation tactics on a captured insurgent, later abandoning him to be executed by an enraged mob, an event that deeply unsettles Harp. Their journey continues as they connect with Sofiya, a crucial resistance leader played by Emily Beecham, at an orphanage. She reveals a haunting truth to Harp: US drone strikes have claimed the lives of many parents of the orphans, leaving him further disturbed. Sofiya guides them to an arms dealer with information about a bank vault containing nuclear launch codes sought by Koval.
As Harp and Leo make their way to the bank, they encounter Koval's men, including several Russian-made Gumps. In a moment of newfound bravery, Harp aids in rescuing civilians trapped amidst a gunfight between Russian Gumps and US forces, while Leo successfully retrieves the codes. However, Koval is conspicuously absent. After Harp orders a drone strike that obliterates the bank and nearby structures, military leadership concludes that Koval and Leo have perished in the blast.
Reuniting with Leo, Harp learns of Leo's ulterior motives concerning the codes; he had been manipulating Harp all along for his own escape plans. After subduing Harp, Leo abandons him on the roadside, where Sofiya's men recover him. Meanwhile, Leo confronts Koval to hand over the codes but kills him when Koval refuses to grant access to a critical nuclear missile silo. With urgency, Harp contacts Sofiya and his commanding officer to reveal Leo's malevolent intentions: Leo plans to launch the missiles at the United States in a bid to stop future conflicts.
Determined to intervene, Harp infiltrates the silo only to discover that Leo has taken control. A confrontation ensues, and Harp successfully disables Leo but not before Leo initiates a missile launch sequence, claiming that his ultimate aim was to ensure the failure of the android super-soldier program. Harp makes a narrow escape just before a drone strike demolishes the silo, resulting in Leo's demise amidst the explosion. In the aftermath, Harp returns to Camp Nathaniel, where he is commended by his commander, who informs him that he is to return home. The story concludes with Harp leaving the base, the weight of his experiences clearly evident.
