The children from a small Moravian village are not happy with the news that a summer camp for pioneers from the town is to be built in their favourite valley. Matúš, the oldest of the children, is particularly incensed. The village children try to make the pioneers' life difficult, someone destroys the dam they built in the stream; in the end, however, the majority of the locals befriend the new-comers. After some time Matúš has a change of heart, having experienced his first platonic love affair with one of the girls from the camp.
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