Year 1955. The border guard Lieutenant Štěpánek lives with his young wife and small son Péa in a Šumava Mountains village near the border. Jiřina Štěpánková has not come to terms with her environment, first of all she does not like her husband's extra shifts, which disrupt their private life. She is determined to return with her son back to inland. The lieutenant is unhappy because of his wife's sorrows, but he is not going to leave the job he likes. Péa loves and admires his father. One Sunday, when Štěpánek is again on duty, Jiřina begins to pack. When Péa learns that father is not going with them, he leaves the house unnoticed and goes towards the border area. In the village a dancing ball is in full swing, but everyone willingly goes to duty. They know it is necessary to find the small boy. Péa carelessly wanders through the forest, but slowly it is getting dark and very cold. Jiřina only now understands what an extra shift means and appreciates the solidarity of her neighbours. The boy is finally found asleep. Overwhelmed by joy, Jiřina sees how selfish she was, and decides to support fully her hard working husband.

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