Police Major Igor Grom is known throughout St. Petersburg for his determined character and uncompromising stance toward criminals. His immense strength, analytical mind, and incorruptibility make him the perfect police officer. However, everything changes dramatically with the appearance of the man in the Plague Doctor mask. Declaring that his city is "sick with the plague of lawlessness," he sets about "treating" it by killing people who had previously escaped punishment with money and influence. Society is in turmoil. The police are powerless. Igor faces difficulties in his investigation, the outcome of which could determine the fate of the entire city.