Germany 1932, constant fights between Communists and Nazis tear the country apart. When a Communist is found dead, the police accuses another Communist being his murderer. But the Communist youth group follows another trail - the murderer left a characteristic boot print at the scene of the crime.

The young architect Hannelore becomes part of the all-male brigade Fröhlich whose members are supposed to build houses at the Strausberger Platz in Berlin. The brigade men drink a lot of beer and are less than thrilled about the new girl. Hanne is the only one who is absolutely delighted with Hannelore. When he starts a drunken fight on May Day, he is arrested and accused of armed robbery. Hannelore immediately convinces the other men in the brigade to help Hanne.