The Gree — Dalton B. Vail

The Kelvans arrive on earth to warn the population about the impending invasion of THE GREE. Will there be time to save the human race? The Gree are a nomadic alien race that searches the galaxy for intelligent life and resource rich planets to plunder and terraform. They know about earth and they are on their way. The Kelvans encountered the Gree on their home planet and were nearly annihilated, but survived and have now come to earth to warn the population and help them prepare for the inevitable battle. Without help from their own kind and their advanced technology, will the Kelvans be able to save earth?