"The humans and Ildirans, having narrowly escaped annihilation at the hands of the Shana Rei and their robot allies previously, are desperate to find a way to combat the black cloud of antimatter of the Shana Rei. The mysterious alien Gardeners, who had helped them previously, turn out to be a disaster in disguise and because of them, the world tree forests are again in danger. The allies, believing they have found a way to stop their dreaded enemies, [test a new weapon], but it's a horrible failure, throwing the human race and its allies to the brink of extinction"-- Provided by publisher.