When you enter the Agroprom Research Institute area you'll notice a stalker ahead of you, calling you towards him. It turns out that Mole and his group are under attack by the military and he wants you to help them in the fight. Follow the stalker towards the first installation of buildings; once you get closer you'll be interrupted by a small in-game cut-scene showing you the area ahead revealing a number of stalkers exchanging gunfire with soldiers.