Wil McCarthy combines two branches of speculative thinking - space travel and biotechnology -- to create a chilling and entirely believable future. In the late 21st century, manmade self-replicating organisms, smaller than the tiniest bacteria, have mutated and swept across the entire inner Solar System, incorporating it into the entity known as the Mycosystem. As the Mycosystem tries to breach humanity's last colonies on Jupiter, the humans try to fight back by travelling to Earth where their enemy first emerged.