Three schoolchildren accidentally find a magical portal in the Holy Trinity St. Sergius Lavra and are carried away into the past. Now their goal is to return home, and for this they need to go through the wonderful forest of the XIV century during the Tatar-Mongol yoke and the Battle of Kulikovo. St. Sergius of Radonezh will help the teenagers.

The heroes of the first part return and team up with the characters of the second part of the Big Trip franchise! But their enemies Python and Vulture are not asleep either! Where it all started, that's where it all ends! And our heroes will win as always!