During World War II.
Because of a betrayal, Soviet Army Lieutenant Avgoust Grieze is taken prisoner. The fascists try to win him over to their cause.
Avgoust refuses. So the fascists spread information, falsely attributed to Avgoust, to the Latvians so that they stop their resistance.
His comrades in arms then consider him a traitor. Avgoust manages to escape from prison.
Soon after, throughout Latvia the news spreads of the appearance of a lone avenger, an intrepid partisan under the name of Kroum.
