In the mid-22nd century, humanity has begun to establish colonies in some of the stellar systems closest to Earth. The story takes place on Okami, a planet which is home to a rich variety of vegetative life. Ten years after settling on Okami, the colonists inexplicably lose contact with Earth and all other human colonies and ships. A few months later they are attacked by previously dormant creatures native to Okami. The mycophytes, as the creatures become known, seem to share characteristics with Earth plants and fungi. Until the attack, humanity had yet to encounter another intelligent species, let alone one with such an unexpected physiology. Over the next few years, an apocalyptic, siege mentality develops in the one remaining settlement on Okami. Further attacks are repelled with minimal losses, but supplies are running short, and there has still been no contact from off-world.