A group of young scientists conducts an experiment, putting themselves in the conditions of the people of the Stone Age. With the help of stone tools, they procure food and fire, and make themselves comfortable in nature.
Germany, the 1930s. A young scientist, Professor Johannes Werner discovers rays of life-giving power. The scientist refuses to give up his invention for military use and, breaking the equipment, runs to the USA, where he hides for a long time under the name of Martini. One day, after being invited to a military industrial concern to see a new European invention, Werner meets his former pupil Huber. Huber, a traitor and fascist, has restored the professor's apparatus according to stolen plans and is demonstrating it as his own invention. Werner rejects the proposal for joint cooperation and, at a meeting in the hall of scientific associations, reveals his real name and resolutely reveals the criminal intentions of the revanchists.
The end of the 1950s. The Chinese passenger plane, following the Beijing-Moscow flight, enters a thunderstorm and makes an emergency landing in the Baikal region. In addition to the Soviet citizen Varvara Komarova, all other passengers are foreigners. Using a stop, they explore new cities and get acquainted with the life, work and rest of Soviet people.
