"I'll be back!" ‒ a teenager named Caster, who was carried away by dragons from his native village, promised his fellow countrymen. In the fantasy world of Sergei Komalov, people are conquering more and more living space from dragons. And those, deprived of their usual habitat, raid villages and steal livestock. Competing for a place in the sun, different clans of flying lizards conflict not only with people, but also with each other. Hoping to save their world, the chosen black dragon Ovi, his friends Erda and Pinto go in search of a treasure cave. The covenants of the ancient sages are inscribed on its stone slabs, which the dragons ask Caster to read. According to prophecies, the future of dragons and humans is under threat. Their world could be taken over by evil aliens, tired of living under the light of the purple moon. To acquire the perfect weapon, Ovi and Pinto undertake a dangerous journey to the region where the sun has gone out. How did the risky voyage end? Has Custer returned to the people? The reader learns about this from Ovi himself.