en Cuevana 3. The team of diesel locomotive builders is struggling to increase output. More efficient welding methods are needed, but all the efforts of Andrei Kostrov and his comrades to design a new welding machine are in vain. On this ground in the brigade disagreements arise. A group of skeptics persuades Andrei to abandon the fruitless search and go to work at the former site. Among the doubters is Kostrov's wife Taisia.