The two half-orphans Reni and Rolf are 13 and 10 years old and they live with their grandmother in Berlin. Their father has died during the war, their mother works at a Baltic Sea port. Here she meets a captain who wants to marry her. When their mother tells them about the planned wedding, Reni and Rolf are reluctant to meet the captain.

GDR and West Berlin in the 1950s. Hans Nettermann, a designer at the "Komet" bicycle factory, is a favorite of the BSG road riders. His dream is to one day ride in a stand-up race. A construction error throws him back in the road race. They work for a long time to fix it. Then he is persuaded to go to West Berlin to become a professional rider. Although he makes it to the top class, he also learns about the scams in professional sport. He marries Marianne, who has followed him and tries to persuade him to return to the GDR, which he eventually does. After some difficulties at work, he is nominated for the first amateur endurance race in the GDR and wins.