Knife in the fish

The year is 2028. For several seasons now, schoolchildren have been spending their time in educational and entertainment centers, where safety and strictly regulated activities are the norm. However, for the young heroes of this story, this is too boring. Craving adventure, they discover a secret passage leading to a basement where a mysterious scientist is conducting research on time tunnels. He is just looking for test subjects, and the friends unexpectedly find themselves drawn into a vortex of exciting events. Together with the Cossacks, they embark on a perilous journey to defeat the Water-headed Monster that terrorizes tavern patrons. They must unravel the mystery of the archaeologists' murders and the theft of Scythian censers. But most importantly, they must find a way back to their own time, as the time tunnels are fraught with numerous dangers.