Secret (1963)

Adventures of the boys of a pioneer camp during a summer camping trip. A new leader, Artem, a geophysics student and hiker, came to the pioneer group. He led the pioneers on a hike, which they had been doing for three summers in a row, in places they had long known and explored. And then the four friends, Gena, Dima, Pasha and Oleg, decided to escape from the group and go hiking on their own, but not just for fun, but for the sake of a great discovery. They dreamed of discovering "state-important ore," which, according to Dima, must be somewhere in the vicinity of Sinoe Lake. Far away from Sinoe Lake, the paths of the squad and the four friends converged. The boys didn't find the ore, though - Dima made it all up - but they did find a legendary tank whose trail was lost during the German-Soviet war. The boys decided to search for the unknown heroes and find out their names. The hike continued.