It is 1955 and the government in Czechoslovakia has declared an amnesty for post-war emigrants. Many of them returned to their families, only young Pavel Kocián's single mother waits in vain for him. Despite her protests, Tomáš Stach, an assembler, is accommodated in her flat as a lodger. Until recently, his fiancée Jana was also waiting for Pavel's return, but she has given up hope and visits Mrs Kocián only out of pity. One evening, an unknown man who introduces himself as Jonáš and claims to know Pavel visits her.

A group of children from 1930s Prague follow the news about the polar expedition of the Chelyuskin, whose members find themselves stranded on a floating crust after the shipwreck. The rescue operation they had planned eventually turns out to be an aid to the striking workers of Děčín...