The first days of the Great Patriotic War. Left without command, young Soviet servicemen Viktor, Artem, Stepan and Roman decide to give battle to the advancing fascists, taking up defensive positions in an ancient, dilapidated fortress, which contains a surviving artillery cannon and a lot of ammunition. None of the guys know the real situation - how far is the front, where are our troops, where to go next? But the four heroes are determined and are preparing to fight not for life but to the death with many times superior enemy forces.