The events of the historical series "Katyusha" take place in 1944. The Great Patriotic War is in full swing. During an attack, Red Army soldiers notice a soldier on the front line. He is severely wounded, wearing a uniform without any distinguishing marks, and suffering from shell shock. He can't remember anything. The soldier is examined by specialists from the Special Department. It is soon revealed that he is Major Egor Petrov, a reconnaissance officer. He went on a mission a week ago and returned without his comrades.