1941. The Belorussian SSR is engulfed in war. In German-occupied territory, Soviet partisans discover secret uranium mines. Here, dangerous experiments are conducted under the guidance of a talented Russian scientist who fled Soviet rule after the Revolution. The scientist is not simply devoted to his work; he is obsessed with completing his scientific research on the energy released by nuclear fission of uranium, as these discoveries could change the course of the war and world history. A former recidivist thief, Aleksey Lavrentev, nicknamed Lyokha-Lavr, narrowly escapes death after finding himself in the thick of the war. Fate leads him to the partisan detachment of NKVD Captain Viktoriya Degtyarenko. Initially, his new comrades greet him with mistrust and hostility, but thanks to his resourcefulness and courage, he quickly earns authority and respect. Gradually, Aleksey learns that the mysterious German scientist is his father, Aleksandr Lavrentev, whom he thought was dead.
