At the amateur talent show the boy, accompanying himself on the accordion, sings a song about Moscow... The plot of the movie is based on the story of the director of the school about how this accordion, once belonging to a cadre worker who died during a demonstration in 1905, has been in many hands before it got to the guys.

The hero - an absent-minded person from Basseinaya Street - goes not to Moscow, but to the opening of a children's railway. The pioneers invite him there. And this time the character finds himself in a lot of funny situations along the way. However, he still manages to open the railway. The picture ends with a march performed by schoolchildren.