In the 1980s, the United States and the Soviet Union inadvertently released tens of thousands of aliens named "Droba" hidden on Earth. Unexpectedly, Droba with the virus caused a fatal infectious disease and was eliminated by the Earth Legion. After Droba became extinct, the Legion was disbanded. Many years later, the former Legion members were accidentally assassinated, and the suspected uneradicated Droba came for revenge. The remaining Legion members must find each other and find a way to fight back before being killed by the Droba mutants.