It is the year 1944. Despite the ban imposed by the German occupiers, students at a teacher training institute in a small town decide to hold a secret ball in the clubhouse of the swimming pool. Lenka (Andrea Cunderlíková) is one of the students preparing for the ball, even though before his departure on a business trip her father has strictly forbidden her to get involved in any such thing. The initiator of the ball is Lenka's friend, the doctor's son Slávek Olejník (Petr Svojtka). While the students are making preparations for the ball, members of a resistance group meet in the boiler room of the Sokol PE organization. They decide to send Vasek Potuzník (Jaromír Hanzlík) to warn a gamekeeper that he is in danger of betrayal, but before Vasek manages to get away, the town is surrounded by SS units that have been catching partisans in the surrounding woods.