The film covers the events of 1896-1905 - from the first revolutionary gatherings to the armed Moscow uprising of workers at Krasnaya Presnya, later called Bloody Sunday. St. Petersburg students Alexander Mikhailov and Yevgeny Svetlov and a peasant girl Varvara Postnikova arrive in Moscow and follow the complicated path of underground revolutionaries.

The film is based on real events and reveals the tragic episodes from the life of the Austrian biologist scientist-materialist Paul Kammerer (1880-1926), hunted by regressive scientists and Catholic reactionaries who committed suicide.