Major Hariev, a State Security officer, manages to learn that the spying center codenamed Citadel receives encoded letters. Sometime later, the Bulgarian agent in the West reports that the spy h as a subscription to the French woman's magazine. The State Security men find a beautician, who received the magazine and delivers it to Ivan Bolyarski, director of an important state department. Hariev follows Bolyarski to his meeting with the Hawk, his associate working in a military unit. The Hawk agrees to deliver the request information for an exorbitant sum of money. Hariev runs into the Hawk and kills him in the fight. Bolyarski is arrested. Major Hariev is planted in his cell. In a moment of demoralization, the agent discloses the secrets of the Citadel to Hariev. Hariev has to go to the Citadel, passing off as the Hawk. He takes a leap in the dark and does not know if he will ever come back to his wife and his child.