Botanica is an island, but almost all of the island is taken up by the Tree. Lillah has come of age and is now ready to leave her community to walk around the Tree for five years, learning all that Botanica has to teach her. Before setting off, she is begged by the dying mother of a young boy to take him with her. But if anyone suspects he carries the disease too, he and Lillah will be put to death.
