
Upon his arrival, he captures a Belter (a worker from the asteroid belt) named Jack Brennan, who is infected by Phssthpok's store of tree-of-life root and is transformed into a protector (or at least a Human variant). The first half of the book follows the path of a Pak named Phssthpok who has travelled from the Pak homeworld in search of a colony of Pak in the distant system of Sol (our solar system). A key plot point is that transition to the protector stage is mediated by consumption of the root of a particular plant called Tree-of-Life, which cannot be effectively cultivated on Earth.



Its central conceit is that Humans evolved from the juvenile stage of the Pak, a species with a distinct adult form ("protectors") that has immense strength and intelligence and cares only about younger Pak of their bloodline. The novel comprises two phases in the same space that are separated by 220 years of time.
