Pennterra is a beautiful and fertile planet and humanity's last hope for survival. But Pennterra is already inhabited. After warning other colony ships to stay away, the small advance colony of Quakers has adapted to life on Pennterra. Heeding the empathic warnings of the native hrossa, they have settled in a single valley, sharply limited their population, and continued to use no heavy machinery in their building and farming. But surviving under these conditions has left the Quakers little time to learn more about their native neighbors. Catastrophe or peace-Tanka Wakan, the omnipotent master spirit of Pennterra, will decide.