Having exsanguinated Prince Yuri's squad in the battle on the Voronezh River, the hordes of Khan Batu are rapidly advancing towards Ryazan. The invasion has begun. The advanced detachments of the Tatars are already prowling the lands of the principality. Pronsk is besieged, Belgorod and Izheslavl are burning. Around Ryazan itself the ring of encirclement is shrinking ever tighter. At the last moment, Prince Yuri sends an embassy led by his brother Ingvar to Chernigov for help. Boyar Kolovrat also goes with him with a small squad and a secret order. Ingvar, who himself wants to become the ruler of the principality, arouses too many suspicions. The threat hanging over Ryazan does not frighten the rest of the princes of Rus', who are busy with their feuds. Everyone is waiting. And only Kondrat Zarubin, whose spirit was transferred into the body of Kolovrat from the twentieth century, knows that this is the beginning of the Tatar invasion. Very soon, all of Rus' will go up in flames. The governor is sure that without help, Ryazan is doomed. He has already taken many secret steps to make the city last longer. And Ryazan stands under the blows of Batya’s hordes, as if it were protected by immortals. By chance, Kolovrat falls into the hands of an ancient secret that can change the course of history. The fate of Ryazan is now in his hands.