A film about the mathematician, academician S. L. Sobolev. Photos by S. L. Sobolev for different years Professor O. A. Ladyzhenskaya speaks about S. L. Sobolev (synchronously). Professor A. G. Fomenko talks about the discoveries of Sobolev (behind the scenes). S.L.Sobolev gives lectures to students of Leningrad University, drives around Moscow in a car, talks about his life and work (synchronously and behind the scenes), with his family, at home, at a meeting with classmates, works at his desk, walks through street of Leningrad, goes to the building of the Academy of Sciences of the USSR. Interview with Academician A.P. Aleksandrov (synchronously). Chronicle footage: a meeting of Chelyuskinites in Moscow in 1934, a demonstration, a sports parade, a workshop of one of the metallurgical plants, children on the carousel. Chronicle footage of the Second World War: the production of shells, views of the city of Leningrad, the construction of aircraft.