The main character of the series "The Lady with the Dog" is Agata Marfina, a pensioner. She used to work as a math teacher, but after the death of her beloved husband, she was forced to leave the school and move in with her daughter. She misses her past, and only her dog Scarlett comforts her. One day, Agata accidentally becomes a witness to a crime. What she saw doesn't let Agata Denisovna rest, and she decides to investigate the murder herself. She is supported by her neighbor Igor and investigator Edik, who was once her student.