On the planet, Yanin becomes a victim of vampires, but his American colleagues help him. They offer to play the plan they developed - to lure vampires with an ultrasonic signal and shoot. Yanin gives the go-ahead to conduct an experiment at the minimum signal power, together the astronauts fight with vampires, but later Yanin decides to look for another way and goes for reconnaissance. On the way, vampires attack him again, but he manages to recover from the disease they endure due to prolonged exposure to air and the ingestion of antibodies. He meets representatives of the intelligent race, and they explain to him that vampires get food for them and are an important part of the ecosystem.