The XIII century is a very cheerful time! Nothing could be easier than the mission assigned to Valdar and Lis this time. They have to go to Novgorod and be present at the meeting of all the great warriors of the Russian land, and then they have to report back to the Institute. The only thing is, in order to get back home they will have to first... In short, do the impossible. There is no such word as "impossible", when we are talking about Valder Kadmil and Lis - the brave operatives of the Institute of Experimental History.
