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).

Upon his conversion to Protector form, Truesdale immediately comes to view Brennan's plan as necessary and completes it by breaking out of hospital confinement and infecting the entire population of Home.

As an aside, it is mentioned that during his sojourn in the outer Solar System Brennan had engineered a genocide on Mars, sending a large ice asteroid to crash into the planet in order to raise the water content of its atmosphere.

The events which impelled Brennan to this action are those narrated in "How the Heroes Die" and "At the Bottom of a Hole", two short 1966 stories which Niven originally published in Galaxy Science Fiction and later collected in Inconstant Moon.

Sidney Coleman reviewed the novel favorably in F&SF; although describing it as really "two long novelettes passing as a novel," he noted that "both halves of the book are permeated with the ingenuity that has been the driving energy of Niven's stories since his earliest work.