The series is loosely based on the eight works of Andrei Konstantinov [ru].
[2] The only character who appears in 9 seasons (except the film The Operative), is Lieutenant Colonel Kudasov by Yevgeny Sidikhin.
The series' theme song is The City that isn't there, by singer and composer Igor Kornelyuk, and lyricist Regina Lisits [ru] .
Part I of the series also features You're a Stranger To Me by Tatiana Bulanova as a secondary theme.
[1] Although the events of the series are portrayed as taking place in the late 1980s to early 1990s, anachronistic objects such as car models, mobile phones, personal computers, signage and media appear in the series; even gravestones with dates from the late 1990s appear.