Soviet scientists have been tasked with developing a new variety of rubber plant that would solve the problem of rubber shortage in the USSR. At a field station in Kyrgyzstan, breeding work is being carried out to modify the local rubber plant Kok-Sagyz. But one day one of the researchers comes across a giant root of a plant that could solve all breeding problems. And then he decides to go on an expedition to the mysterious Batyrlal-Jol gorge, where this plant came from.