The action takes place in Moscow in 1956 and tells the story of four women who are connected by a military past: work in the GRU special department. They converge again to conduct investigations and help the investigating authorities in particularly complicated cases. Possessing phenomenal analytical skills, Irina, Anna, Sofya and Katerina, risking themselves, as well as the well-being of their own families, catch criminals who threaten the lives of ordinary people and the whole country as a whole.