The enemy is smart and cold-blooded. His arsenal includes logic, perseverance and precise calculation. He is confident that he knows how to defeat us in this fight. But the enemy does not take into account one thing: standing in his way are super-professionals in their field, people of risk, honor and unbending will - Soviet counterintelligence officers. The Soviet station in the West receives a signal about a data leak from a closed research institute, leading developments in the field of microbiology and virology. The group of KGB Major Mikhail Koltsov is tasked with identifying and neutralizing the “mole”. The operatives make sure that formally all instructions for protecting state secrets at the enterprise are observed. Then how does a spy manage to transmit information? Finally the major finds a serious clue. To make sure that this is the same channel, Koltsov puts his own life on the line...