They're my favorite of all time, they take place in the Soviet Union post-Great Patriotic War, they follow the "Gangster Fighting Division" (not great translations being honest) of the Moscow police. The main enemies of the films are gangsters in general, though mainly it's focused around two things, the murderer of a woman, and the gang the "Black Cat" (черная кошка.) They are very revealing of Soviet society as well. The ex-soldier Sharapov asks if they could interrogate a presumed gangster, but they laugh as you are only they were only allowed to interrogate proven criminals. It also reveals how everyone was drafted during the war and people are still recovering though living a happy life. (Ex: the female police Sharapov officer meets while handling a case with a baby in the second film.) Over all really love them, watch them!