This is a poetic film set in the times of Lenin's NEP. A ballet dancer steals a brooch and gives it as a present to another dancer. This is a crime of passion. A mysterious black ball is after the heroine. She runs away from it and manages to give the brooch in an exquisite pirouette movement, as shiny as diamond facets. What gives a stone its dazzling luster are its polished facets. But the real gem is love, and it's much harder to get than any diamond in the world.