Captain Velkov was sent chief of a border post near the village of Novi Izvor, where he was a partisan. In Novi Izvor a celebration is being prepared to mark the switching on of the electricity. Saboteurs cut the cables, killed the watchman and set fire to the machinery on the farm.

The university student Bobchev joins a youth brigade. The commander's council entrust Bobchev with a literacy course for members of the brigade. Velizarov and Monkata arrive in the camp to carry out sabotage. They place explosives on the dam, and attempt to win Bobchev over by means of intrigue. There is a storm: the camp is put on the alert. Everyone joins the rescue work at the dam. After a long struggle with Velizarov, Bobchev cuts the burning fuse of the explosive. The dam does not yield to the pressure of the flood. Everymen sing in Jubilation.