The GRU began to receive strange encryption messages from the American agent Major Kustov. To unravel their meaning, Colonel Buzgalin, an experienced intelligence officer and psychoanalyst, arrives in the United States. When the agent's obvious insanity is discovered, Buzgalin takes him out of the USA, delivers him in a roundabout way to the USSR, subordinating the crazy Kustov to himself by at times plunging his brain into the Middle Ages, into monasticism, where brotherhood coexists with unquestioningness. During his wanderings, Buzgalin fell in love with his monastic brother so much that on the eve of the trial he entered a meeting of the medical commission and, involving Kustov in the Middle Ages, saved him from imminent execution - at the cost of his own career. The Soviet Middle Ages are the 70s. The war was cold then, and weapons were verbal. The struggle for global justice looked like the intelligence activities of states divided into two camps: capitalist and socialist. Spies had mothers, got married and divorced, gave birth to children...