The protagonist of the detective-drama series "Leon" is Grigory Leonov, a young single father who serves as a police major. His beloved wife died several years ago in front of him and their little daughter Masha. Since then, the girl has been plagued by panic attacks and refuses to be separated from her father even for a few minutes. The man has to take his ten-year-old child with him to work. Of course, neither his superiors nor his colleagues approve of this, especially when it comes to dangerous investigations, but Grigory has no other option.