The major, an employee of the operational department of a secret government organization, the Bureau, engaged in the study of anomalous zones and phenomena, finds himself in one such zone that is beginning to form in the Siberian taiga. Trying to find out the reasons for its occurrence, he goes on the trail of terrorists who prepared an explosion in a mothballed secret laboratory that was working on the creation of military viruses. With the help of army units, the terrorist attack can be partially localized, but both of these events are only diversionary maneuvers for the enemy’s main operation. The terrorists' traces lead to the Caucasus, Ukraine, Wahhabi fanatics and US intelligence services, but there is no direct evidence of their participation in the terrorist operation. It was a secret war with an invisible enemy - a war of shadows.