Zarya-5 is the codename of a secret underground facility built in 2004 near an abandoned Elchansk town. In theory it was an expeditionary unit of Engineering Experimental Center Zenith-2 (a successor of the pre-war Zenith from TAFR system), but in fact it was funded and supervised by the Interdepartmental Committee for PVT.
Although Soviet scientists extensively studied the anomalies that appeared after the war of 1962, a sound theoretical explanation has not yet been found (there are many theories from off-world intervention to the Antichrist).
The main goal of this secret lab was the study of physical anomalies of unknown nature that appeared on the territory of the former Moscow region. Scientists from Zarya-5 sought and cataloged unusual phenomena, determined coordinates of various anomalous fields, observed their seasonal changes and so on.
In spite of high level of security the lab was completely devastated in autumn 2012 in a sudden attack by unknown and heavily armed forces. On the night of the attack, most of the lab security personnel was sent to a nearby defense perimeter due to an alarm there (which was later found to be false).
As a result of this, the entire lab crew was murdered, and valuables including expensive equipment and rare artifacts were stolen. Only two teams of scientists and technicians, who were outside in nearby swamps collecting gravitational ignitrones and samples of inhibited plutonium at the time of the attack, managed to survive.
The main hero of the game will find only the ruins of the plundered lab, pieces of broken equipment and remains of its defenders. As you can see on screenshots, there is no one left in Zarya-5 except the ubiquitous rats.