A Soviet cruise ship "Evgeni Onegin" is carrying cages with tigers and lions for a Soviet Circus. One loose monkey unlocks all cages, letting the tigers and lions out. Poor passengers and crew have no place to run. The captain abandons his post out of fear, and the monkey takes over the captain's post. The ship gets under total control by the tigers and lions. Only one lady is standing up to the challenge. Her name is Marianna, she loves animals, and she takes the situation under control.

For the third year, the expedition has been searching for the causative agent of an infectious disease rampant in the Ussuri taiga, where a major construction project is about to begin. Meanwhile, the enemy seeks to destroy the fruits of years of labor of Soviet microbiologists. Young scientist Vasily Zheludev exposes a master saboteur and forces him to flee into the taiga.

Moscow during the Sixth World Festival of Youth and Students. Performances by circus artists from different countries on various stages: at the circus, in the Gorky Central Park of Culture and Leisure, at the operetta theater, etc.

Documentary film about the Soviet circus with the participation of Yuri Nikulin, Zinovy Gerdt, Yuri Durov, Mikhail Rumyantsev and Irina Shestua.