During winter break, the fifth “B” students are supposed to go on a historical field practice. Each of them must choose some secret from the past and unravel it, as well as shoot a film about it. The sisters Masha and Natasha Bely want to learn the secrets of Bluebeard and the Iron Mask; Alisa Selezneva— the Tower of Babel and Cleopatra. Arkasha Sapozhkov wants to find out why the dinosaurs became extinct. And the main hero of this story, Pashka Geraskin, is not opposed to paying a visit to the troglodytes. Like the rest of his classmates, he’s in for a great number of incredible adventures…