In the tumultuous year of 1933, a young boy, left orphaned amidst the Ukrainian Holodomor, escapes from his orphanage. He finds refuge with a Red Army unit and is kindly embraced by its commander, who names him Leo Demidov. By 1945, Leo has risen to the rank of sergeant and achieves national fame when he is immortalized in a photograph as he plants the Soviet flag atop the Reichstag during the Battle of Berlin. This heroic act earns him the prestigious title of Hero of the Soviet Union.
Fast forward to 1953, Leo is now a captain within the Ministry of State Security (MGB), residing in Moscow with his wife, Raisa. His unit is tasked with tracking down dissidents, but their operations take a tragic turn when they arrest a veterinarian named Anatoly Brodsky. During this arrest, the reckless but ambitious officer Vasili Nikitin, who harbors resentment towards Leo, shoots a farmer and his wife, leaving their two little daughters orphaned. Outraged, Leo confronts Vasili, but tensions escalate as Vasili finds himself in charge of Brodsky’s harsh interrogation and ultimate execution.
Vasili’s betrayal goes further when he implicates Raisa, a dedicated primary school teacher, in his report to their superior, Major Kuzmin. This forces Leo into a heart-wrenching predicament as Kuzmin demands that he investigate his own wife, who has just revealed her pregnancy. Amidst this turmoil, tragedy strikes when Alexei Andreyev, another officer in their unit, loses his young son Jora, found dead under suspicious circumstances that authorities refuse to investigate properly, deeming it merely an accident as per Stalin's beliefs.
Defying orders, Leo investigates Raisa's innocence and boldly refuses to denounce her. The couple is ultimately arrested by Vasili, enduring a humiliating internal exile to Volsk where Leo loses his rank and is demoted to a lowly policeman while Raisa is forced to work as a school cleaner.
As fate would have it, another child’s body is discovered near the railway in Volsk, echoing the circumstances of Jora's death. Leo deduces that a serial killer is on the loose, embroiling them both in danger once again. After a series of harrowing events, including troubling revelations about a local ticket collector and a violent confrontation with authorities, Leo and Raisa grapple with their loyalty to each other and their desperate quest for justice.
Their clandestine journey leads them to Rostov, where they uncover the identity of the serial killer, Vladimir Malevich. In a climactic encounter, Vasili tracks them down but meets his end in a brutal struggle with Leo and Raisa. Cleverly, Leo spins the narrative to portray Vasili as a hero, thus securing their own safety and reinstatement in their positions.
In a time of possible change with Stalin’s demise, Leo is offered a promotion, but he instead proposes the formation of a dedicated homicide division, emphasizing his commitment to justice. With the help of General Nesterov, Leo and Raisa take a poignant step forward as they decide to adopt Tamara and Elena Okun, the orphaned daughters of the farmer, uniting their family amidst a backdrop of political upheaval and personal redemption.
