Ring (1973)

Investigating the murder of a cash-collector, Major Isaev, a former boxing champion, comes to the conclusion that the killer is a boxer. To catch the criminal, Peter Isaev takes an unconventional decision. He applies to participate in the city's boxing championship, hoping that the criminal will probably come to watch the former champion fight. Isayev has to overcome each stage of the championship with difficulty: it has been five years since he left the ring...

Mystery