Ring of Infinity. Divide and conquer

Time travels continue, and the five-grader Dacha Smith and his best friend Sir Frost are waiting for new tests for the sake of saving the future world. Straight from the ship & quot, Santa Maria & Quot, Christopher Columbus they fall into medieval Paris on the eve of his siege with fierce Vikings, surrounding their huge delices a little fortress on the island in the middle of the Seine. While Duck, Sir and their friend-historian Rick convulsively try to understand what historical mistake they have to be corrected, the situation is rapidly deteriorating. As a result, the guys turn out to be on different sides of the barricades: Duck - in the Viking camp, in Sir and Rick - behind the walls of Paris. And they have no ideas, what to do